René Degiovani
6, rue Castel
83000 Toulon

Mr G has a right hemiplegia as well as a Broca’s aphasia. The scanner shows a cortical-subcortical lesion centred on the F3 and the BDAE severity score is 2. Results in picture naming are in the average range but word retrieval difficulties in expression are important. Agrammatism is present, two-word groups most usually being restricted to two or three units, articulation is still deficient and oral and written comprehension are not perfect.

It is also possible to introduce Mr G this way:

Since his stroke, Mr G has major difficulties in expressing his thoughts. He had to leave his job as an engineer. He refuses to leave his house therefore he does not meet anyone who could recognise him. He spends his time in his garden, does not communicate with his wife in any other way than by giving her orders. He receives three speech and language therapy sessions each week and participates assiduously in the proposed work. He has an exercise book and demands to have exercises to do. He totally refuses to speak to the speech and language therapist on any subjects other than "work". His improvement in rehabilitation has been notable over in the last two years.

Mr G probably represents a real failure in speech-language pathology intervention. Subsequently baptised "Rehabilitation Nobel prize" (Ponzio and Degiovani - 1986), this case crucially shows that a certain recovery in oral and written language does not necessarily correspond to an improvement in communication and quality of life of the patient and his close relations.

We probably all have been witness and/or actor of such a mess. Do we have measures to avoid it?

In fact, through this example, we are sent back to consider our role as speech and language therapist and to the limits of our profession.

In the last few years, there has been a tangible evolution in the therapeutic approaches to aphasia. One just has to follow the specialised literature in the field (particularly Aphasiology, but also Topics in Stroke Rehabilitation) to see a major new direction in the written documents. Roughly until 1995, all the articles had the same required scientific format: strict presentation of a case, experimentation, results and discussion. Of course, in that game only what concerned language stricto sensu was approached. Then we have seen flourishing and multiplying (to the extent of filling complete journal issues) articles exploring other ways and forums on "human" themes.

That phenomenon has obviously not been generated suddenly. It is in the 70’s and 80’s, under the influence of Martha SARNO then Audrey HOLLAND that the first germs of that "alternative" reflection were born. Noting our narrow view on the scope of aphasia, the limits of our rehabilitative possibilities and the sometimes weak impact of our intervention on the life of aphasic persons, some authors have proposed a functional approach based on communication. Some assessment tools, such as the PICA, the FCP or the CADL, were created in those conditions. P.A.C.E. therapy also came from the same current. In the 80’s and 90’s, this way of thinking "differently" was confirmed and grew deeper.

Of course, the notion of "managed care" sweeping the United States obliged speech and language therapists to drastically modify their behaviours. To alleviate the downsizing and the reduction of budgets allocated to rehabilitation, they had either to live in penury or innovate. From that, when classical rehabilitation may only last a few weeks, some questions inevitably rise:

- What should be proposed after the patient is back home?

- What type of intervention is best to help the aphasic person?

- Should speech and language therapists be the only people to communicate with aphasic persons?

- How could we measure intervention efficacy in speech and language therapy?

At the same time, the "functional" reflection has been taken over and prolonged by the issue of the W.H.O.’s (World Health Organisation) activities. It is probably in the functional rehabilitation field that these works, which we will explain further on, had the biggest impact. Guylaine LEDORZE, from Montreal, is definitely the one who most clarified and optimised that approach.

Finally, an even more psychosocial current, an initiative from Ruth PATTERSON, Aura KAGAN and John LYON, proposed a totally alternative approach to the way we are practising now, like the "Aphasia Centres" of the Toronto region.

With the passage of time, conceptions have been profoundly modified, allowing a renewed approach in that field of intervention.

Yet we note that in France, and probably elsewhere in Europe, our way of working with aphasic persons has hardly changed. Of course, when in France we read thesis written by speech-language pathology students in their last year, who could be the barometers of recent thought processes, a real evolution is noticeable: writings referring to a functional, even communicational approach, are frequent. Some of them, like Hélène DARGENT’s thesis about partners’ training, even bring real novelty to the field.

However the training, throughout the examples we obtained, still is fundamentally marked by classical rehabilitation. Reference to the P.A.C.E. is now usual, but in the same vein as reference to neuropsychology, that is to say like simply adding on items to our "perfect little therapist" kit. A paragraph on alternative communication with global aphasics is often introduced. Probably a brief moment is also dedicated to aphasics’ associations.

Nevertheless, the essence of our role remains inviolable: to restore language to the aphasic person.

It is that same preoccupation that daily governs hundreds of sessions addressing that pathology.

Justifications, or rather explanations, exist:

- There is of course the imprint of the medical world on our paramedical profession. How is it possible to explain to a general practitioner, who hardly knows what aphasia is and has no idea about its real consequences, that he should have a "conversation" with the aphasic or that it is useful to discuss with him about a television programme? He is in the "scientific" world of medicines.

- The relationship maintained with funding agencies is of a similar type. How can we obtain an hour’s appointment with the aphasic and his/her neighbours to optimise communication? How can we classify an act considered as social in the light of the referring medical appointment?

- Also, why change our habits when aphasia (and numerous other pathologies) opens up a right in some way to lifelong rehabilitation. Some doctors, prescribing or consultant, convinced of their medical certainties or of the balance of social security accounts, raise their voice refusing extra time, that is most usually accepted after discussion. However, the main tendency is the "maintenance" of the aphasic’s language, which constitutes a notion neither attested by studies, nor operational.

- The scientific gloss of French (and francophone) works on aphasia, which were for a long time centred on an anatomical and clinical perspective beloved by the remarkable Blanche DUCARNE, and then centred on a recognised neurolinguistic school, is most certainly an additional factor unfavourable to the introduction of more "personal" approaches. Those works of globally recognised quality probably "marked" numerous generations of speech and language therapists in the way they conceived aphasia.

- We should not neglect the apparent "simplicity" of the new approaches. On one hand, there would be the highly technical assessment and rehabilitation exercises focused on language, with a very specific vocabulary which is certainly disconcerting for the non-specialists (including the patient and close relations, but also the prescribing doctor). On the other hand, there would be "communication" that some would willingly limit to convivial chattering or to a drawing-room conversation (which is obviously far from the new proposals...).

- Let us as well bear in mind an initial education favouring the experience of predecessors rather than an open mind and intellectual curiosity, particularly towards the Anglo-saxon literature.

It is not at all a question of rejecting all the therapeutic arsenal at our disposal to try to fight against (or to bypass) the aphasic person’s language deficits. Even more, seeing ourselves the state of training sessions, we recommend better quality initial and continuing education as regards rehabilitation techniques. To possess the largest range of exercises corresponding to the large variety of cases we meet is a fundamental requirement. How many speech and language therapists in Europe master the therapeutic approaches proposed by Sally BYNG, Patricia HELM-ESTABROOKS or Marie-Pierre DEPARTZ, or the pictographic possibilities offered to global aphasics to provide an outlet for their expressive difficulties? Who, amongst all speech and language therapists, knows and applies seriously and wisely all the possibilities offered by the neuropsychological approaches, for example in the field of written language?

Whatever the quality of our language therapy, that approach clearly remains incomplete and insufficient. How many aphasics will retain significant language problems which will more or less modify their way of living?

Anne Wells (Aphasiology, 1999) recalls SERVAES’ remarks (same issue), indicating that:

"Six months after the stoke, 12% of the survivors objectively remain aphasics when 44% of the patients and 57% of the caregivers think that language is still abnormal..."

She adds "What is the value of such an objective assessment when it is so little confirmed by the patients’ and the caregivers’ perception?".

How many aphasic persons will carefully and assiduously take speech and language therapy sessions long term, especially if they are taking place at home, when they do not speak to anyone else? How many global aphasics, walled almost in mutism, will search in vain for images far from any life reality? How many partners and close relations will lose hope, not being able to help the aphasic person in any other ways then copying therapy?

We have an immense responsibility towards those patients who put their future in our hands.

We should not accept any more such a misunderstanding consisting only in giving technical exercises in the face of human and familial disarray.

We should not accept any more the idea that language therapy will necessarily lead to an improvement in the aphasic patient’s quality of life.

We should not any more answer the aphasic and his close relations’ questions and distress with a standardised therapeutic answer.

As we are now able to do in therapy with dyslexic children, we ought to achieve a genuine revolution in our basic intervention principles.

Here, the aphasic person should become the centre of our intervention, regardless of the language pathology. Referring to the WHO’s work (1980) is probably the best way to make that inevitable way commonplace for us. Insofar as those concepts remain very limited in Europe, allow us to briefly recall them:

The approach is based on three elements:

- deficit or the deficiency:

In the case of aphasia, this refers to the neurological disorder and the language disorder resulting from it.

- incapacity:

This refers to a restriction or an obstacle (linked with the deficiency) in the realisation of an activity considered as normal for a person. In the case of aphasia, it could be for example the difficulty or the impossibility of writing, answering the phone or conversing with someone.

- handicap:

This refers to what we could expect from a person of the same age and of the same social and cultural background, and it is obviously linked to incapacity. This notion is therefore characterised by a discord between the actual performance and what the person could obtain or achieve before. For example, it could be the loss of a job, the anxiety meeting new people or the difficulty getting in touch with a partner.

Conceptualised that way, aphasia not only affects the person’s being and personality but also his or her family. It is in that way that we could talk about it as a "family illness" because communication is obviously not a solitary act. Throughout the aphasic person’s handicap, it is his or her entire environment that is disrupted daily in its relationship and its organisation.

When we regularly meet aphasic persons, how is it possible not to be sure that our intervention must concern those three WHO elements and that any other way will miss the essential and seem a little sterile? That we take care of language is obvious, that we try to preserve it at its best or to revive communication (in a structured manner) seems easy to conceive and that we try to anticipate handicaps resulting from the disorders (for the aphasic person and his/her entourage) is also logical.

Of course, some voices will rapidly rise to put us back in our place: rehabilitation of words is the concern of speech and language therapists, action on the world is the concern of psychologists and social workers. But this would be failing to recognise reality:

- Reality of the life environment. If the aphasic person often stays a short period of time in a Functional Rehabilitation Centre or in a Day-care hospital, it is when the person returns back home that the stakes will really be obvious. And only speech and language therapists have access to that environment.

- Reality of the disorder. Of course many aphasic persons, but also their close relations, go through some discouraging moments, even depression. But studies show that depression exists for most of the patients with severe illness, particularly in the case of a stroke without language disorders.

- Reality of the stakes. A complete regaining of language would obviously mark a return to the previous life even if the stigmas were remaining, but this is rarely the case. It is around language, communication, relationships with others that is built the distress of the aphasic person, his or her partner and close relations.

Of course, our training does not prepare us to face, in such an extensive manner, the damage arising from aphasia. "The speech-language pathologist knows of course how to treat the language disorder but is rarely trained to intervene in order to diminish the social handicap imposed by aphasia." (A.HOLLAND, 1996)

Does that mean that we should give up that field?

In order to help brain-damaged persons to reintegrate into personal, professional and social life, the notion of "case-management" exists. Professionals from the social or medical world (depending on the case) are specially trained and aim to guide them to limit as much as possible the effects (whether physical, linguistic, psychological, social, legal, or...) of their new condition. Results are often very instructive and demonstrate that taking charge of the person as a whole is rewarding. Also claiming to take charge of patients with Alzheimer’s disease was present long before generalised training on the subject.

How can we deny that speech and language therapists have the responsibility to see the aphasic person as a whole and the right to adopt an integral attitude towards that person?

To restore the language as much as possible,

To maintain communication,

To fight against the consequences of aphasia.

These are our three tasks and our intervention must necessarily take all these dimensions into account. It should not be limited to words but should concern the totality of the aphasic person’s world.

It is at that moment that we will make our "opinion" on the "case" and that the fundamental choices concerning the intervention objectives will be made. After that, we will be on our joint path with the aphasic person and going backward will be difficult.

Assessment naturally includes the first meeting with the aphasic person and his or her close relations. As in any therapy, that first moment could be crucial for the continuation of therapy. As far as we are concerned, we choose not to directly assess language on the first meeting. We prefer to listen to the patient, his or her partner and close relations in order to find out about their way of communicating, exchanging and behaving, aside from their language of which we will have our first direct experience, and to try to form an idea of the impact of aphasia on that group.

After that first valuable contact, assessment must necessarily have three priorities and be founded on well organised objectives. For that, we must have a baseline in the three fields so we can eventually evaluate and adapt our intervention.

We are here on a very well established topic. The language assessment, gradually achieved in the first sessions, should above all allow us to draw up the framework for our language intervention. It should also be a reference point for evaluating our practice, which remains an exercise too rarely done.

This field is not as well defined: there are of course some standardised assessment tools like the CADL or the PICA. Not very well known, even less so in France, they seem to be of a very relative interest to the present exercise. In our view, description and comprehension of the aphasic person’s communication is better achieved with non standardised elements. Besides, there is a serious matter of dispute between those who would necessarily want to quantify the state of communication and those who would rather emphasise the quality of the description. For the former, everything surrounding the aphasic person would be taken into account only if it were possible to measure it, which seems difficult and limiting, as shown by some North-American tools. Perhaps is there a middle way between quantitative and qualitative approaches? For example, in a questionnaire, one of the points judged as fundamental can be finely analysed and described, being eventually used as a reference point for future improvements.

For example the P.A.C.E., frequently used in rehabilitation, can also be used in a different way to become an excellent assessment tool, which provides the double advantage of precisely describing a communication situation in all its diversity and of allowing a precise, almost mathematical, analysis. By simplify the methodology, it is possible, easy and less traumatic for the patient to use it to appreciate the scope of communicative possibilities and the variety of tools used. Using that first approach as a baseline, it will subsequently be simple to evaluate changes.

Communication questionnaires, filled out either by the speech and language therapist, the partner, close relations or the patient, are definitely irreplaceable. Numerous versions exist but without any standardisation, the best one is without any doubt the one we create ourselves with our experience and some borrowing. They allow us to know the aphasic person’s previous ways of communicating, whom he or she was communicating with and his or her choices of communication. The questionnaires also concern the present by bringing to the fore the hitches that now hinder communication. We will then clearly see that the disorder concerns more than just language. Here as well, it is possible to choose one of the points and describe it strictly to use it again in a future assessment.

This expression is now fashionable in several fields and could in the future be the required filter for all our rehabilitative interventions.

Because what is the most important thing for a person suddenly hit by aphasia? Is it the number of paraphasias or the impossibility of retrieving a specific word or is it the fact that, because of the linguistic disorder, he will not be able or will not dare to go and buy some bread or answer the phone? The consequences of aphasia for every moment and life-situation often go beyond the severity of the disorder.

" It is simplistic to consider aphasia in an isolated manner without being interested in the meaning the person gives to that experience. " (G. LEDORZE - Aphasiology, 1999)

Without doing ‘cheap psychology’, our understanding of the real burden the aphasic person and his or her relatives carry is indispensable to avoid missing the essential point. The family rearrangements, the loss of a role and (sometimes) of power, the drop in self-esteem, the loss of confidence, the isolation and even the psychic confinement, all that could happen to the aphasic person and that is the real risk for him or her.

Several lists exist defining the devastating effects aphasia can have on character or personality. Some charts are even easy to use with severe aphasics. It appears fine to establish our own chart in this field which is not well marked out for us and even to describe in writing the supposed state of strengths and weaknesses.

If the evaluation clearly constitutes the moment that will shape our way of conceiving things and trying to act on them, what could be the strong points and the tools for bringing all our objectives to successful conclusions?

- Knowledge and mastery of a large panoply of therapy techniques "against language disorder" is essential. What is the point of a detailed assessment of linguistic disorders if we do not possess the corresponding pertinent and diversified therapy tools? Our therapeutic role would become insignificant if we were not showing our capacity to reduce aphasic disorders. When we are aware of the diversity and specificity of the proposed techniques in each country, sharing these techniques across Europe would be beneficial.

" I slowly realised that the essential of my distress was due to my ignorance of aphasia " (P. MONTGOMERY-WEST, aphasic’s spouse - Topics in Stroke Rehabilitation, 1995, 2,3)

Aphasia remains and will remain misunderstood because at first sight, it is a "discrete" disorder (in contrast with physical or mental handicap) and the persons affected do not easily occupy the front stage!

Because of this there is some sort of mystery surrounding it for everybody, including medical staff, but also and mainly for the aphasic person and his or her close relations who will truly fight only when they clearly perceive what aphasia is (and what it is not) and its consequences. " The understanding of the stroke and of aphasia is an important point in the capacity of therapeutic involvement. It is just as necessary to identify the capacities and the strengths than to show the deficits and loss. The caregivers must know what is still possible as much as what is lost. " (Anne WELLS)

Handbooks, more or less detailed and more or less popularised, do exist. To synthesise them is often useful but they usually are not enough. They must be given with a written personalised description for the close relations which will firmly root the disorders – which are otherwise unknown - in reality. A discussion with the close relations, repeated if possible, is necessary to explain aphasia and its consequences. When the aphasic person wants to resume communication with the outside world, giving information to other caregivers is also useful if the person accepts.

Most of the time, aphasia affects people over sixty who have usually been married [or with a partner] for several decades. We then understand better the double challenge that the partners are facing: maintaining the privileged relationship beyond the disorders and becoming a daily caregiver. For younger aphasic persons, sadly more and more frequent, difficulties are even larger because they might have young children, the partner is still professionally active and the matrimonial roles are different. Besides, it would be very useful to look deeper into those "new aphasics" who have life conditions (from financial aspects to separation problems and difficulties in raising the children) far more problematic than those of older persons already retired from active living.

The partner’s role (naturally more often the wives), but also the consequences of aphasia on their personality, their emotions or their lifestyle, has been widely described in the literature of the last few years.

Our role here is to anticipate handicaps and break-ups that could be the consequence of the incapacities and handicaps of the aphasic person. Information, as personalised as possible, is essential. It must be repeated if necessary.

The speech and language therapist is often the only person able straight from the start to establish communication with the patient. However, as soon as possible, she or he should train the partner (or other possible caregivers) not so they can repeat therapeutic exercises but so they become efficient communicative agents by showing them the strengths and weaknesses of the aphasic person’s communication. That training is without any doubt almost as important as the language therapy itself. As a matter of fact, by its technical character and provision of suitable weapons, the training allows the partner to maintain the conversation, to go back to family stability and to get stronger in that continuing struggle.

" Our difficulty is to get the partner to realise that we know the "right way" to communicate while he or she has been living with the newly aphasic person for years, sometimes decades. (M. ODDY, Aphasiology, 1999, 13, 12) "

This "training" also allows the reduction of unrealistic expectations and inappropriate attitudes developed by the partner, often linked to a certain underestimation of the aphasic person’s difficulties, as is shown in some studies. Our attention should also focus on the new role that (voluntarily or not) the partner is facing. Attitudes that we noted (and wrote about in a chapter of "l’Aphasique") like overprotective or rejecting behaviour could greatly reduce the aphasic person’s efforts to fight.

We should pay attention to, and even get involved with, the different phases leading to ‘language mourning’ allowing them to rebuild their lives. That acceptance, impossible at the beginning, will gradually be at the heart of family discussions and behaviours. Here again, as with individuals with traumatic brain injury where that element is central, we ought to accompany the aphasic person, his or her partner and close relations to help avoid too negative attitudes.

Meetings with other partners, unfortunately so rare in France even in aphasic associations, should be a necessity as is shown by the interest in such meetings from parents of children with traumatic brain injury or dysphasia.

If the first step in the reconquest of communication happens with the partner, and is sometimes limited to that in the elderly, only renewal (or creation) of links with others will be synonymous with complete success for the aphasic person. Nevertheless, the step is sometimes big, between the incomprehension and even mockery of some individuals, the lack of interest from others and the obvious lack of confidence in the aphasic person. The preliminary drawing up of a list of names of the people the aphasic will communicate with should allow us to act on that level. By meeting those privileged communication partners, by informing them, by organising if possible some meetings and by showing the importance of those links, we must try to be the ‘cement’ of that new construction.

Another area, just as important, is the meetings between aphasics or between partners, through organised structures. Even though it is in France (in Lyon in 1976) that one of the first aphasics associations in the world appeared, things here have not really taken off and there are only a few hundred persons joining such associations, often with very different objectives. One chapter of the book "l’Aphasique" written by M. HUBERT and R. DEGIOVANI showed in 1991 difficulties of those structures. Even though they are not perfect, we should be present in their creation and running and we should, as much as we can, encourage the integration of "our" aphasic persons in those antechambers of real life. The notion of "guide", proposed by the Fédération nationale des aphasiques (F.N.A.F.), is well adapted to our role.

Perhaps we should imagine other ways for the transition between home and real life, with progressive integration of other persons and a gradually fading role for the professionals. Even if the American aphasia centres can hardly be transposed to Europe, a few guidelines could be useful as a model.

The preceding paragraphs were insisting on our role to maintain and open communication in the aphasic person’s world.

There is a domain at the cross-roads of language, communication and the world that must constitute a real key to success for our intervention. In day to day life, conversation is an essential moment to get in touch with others, to express ideas - meetings with intellectual, affective, convivial and, in short, human meaning. Conversation is also for the aphasic person a revelation of his or her linguistic competence, however affected it may be.

Assisted conversation must constitute a significant feature of our intervention because it allows us to intervene on several levels:

- Incite the aphasic person to express information, ideas, opinions and feelings in real terms and not as an unequal exchange as is often the case in therapy.

- Create conversational opportunities. For that, the speech and language therapist must accept to leave his or her therapy mantle to become a simple human being, willing to exchange. That implies some sort of personal commitment not always wished for and most of the time difficult to master on a technical level and even more on a personal level. It is not easy to "change hats", from the technical to the convivial therapist with the dangerous possibility of getting too involved in the family.

- Conversation is altered not only for the aphasic person but also for the person he or she is talking to. Some studies have shown that someone talking with an aphasic person drastically changes his or her way of conversing: he or she will control the subject of conversation and will avoid subjects perceived as too complex or uncertain. He or she will often limit the conversation to what is already known (just like in therapy, except when using the P.A.C.E. method). Our role to explain and to train must be strong without spoiling the necessary spontaneity of the person talking with the aphasic.

However, why and in what way is the conversation assisted?

First of all, it is assisted to optimise the conversation that is no longer natural for the aphasic person and the people he or she is talking to. Some indications could then be useful depending on the case:

- As for physical handicap, it is necessary to improve access. In aphasia, it is the access to conversation that should be increased. We should start by limiting the obstacles: surrounding noises and especially television, the place, the moment of the day... As for encouraging conversation, opportunities are not missing as long as in our speech-language pathology role we know how to play an active mediator role.

- We also ought to create a general atmosphere favourable to conversation where the aphasic is considered as a thinking and co-operative adult and not as an infant because of his or her reduced language. That particularly unhealthy attitude must be vigorously opposed, including in our own attitudes. Audrey HOLLAND has written " that we should talk to an aphasic person (usually of a certain age) as we would do to our own grand-parents with respect and dignity. "

- If a conversation is started, the person talking with the aphasic must pay attention. It is not a charitable act to listen to an aphasic person but a communication act which must benefit both parties. For us as well, to get involved in a conversation takes time. We ought to take that into account in the session management because there is nothing worse for the aphasic person than the conversation being interrupted by the individual he or she is talking to.

- The emotional impact of aphasia is often very strong. Irritation, cries and swear words are not rare. They ought to be integrated by the person talking with an aphasic as normal factors.

It is also necessary, even more so than in classic therapy to keep in mind (and to put in action!) some more technical points:

- In particular, it is necessary to clarify the facilitation we can provide to the aphasic person. On one hand, some aphasics can hardly bear - and therefore will not accept - being helped by the person they are talking to. Just the fact of guessing a word could be unpleasant to them. On the other hand, the type and level of facilitation must be "discussed" with the aphasic person because his or her autonomy is involved.

- Comprehension, in both meanings, must be the object of a lot of attention: the speech and language therapist must admit his or her incomprehension and should make sure of the aphasic’s understanding. To simplify the syntax is not often very useful but adding non verbal information would help more. In the same way, it is better to add pauses to the discourse than slow down the speech rate by dragging out words.

Let us definitively erase from our mind the suggestion that aphasia is only a severe language disorder for which a therapy technique could constitute a satisfying answer.

Aphasia is above all a psychosocial handicap affecting the aphasic person as much as his or her partner, close relations and environment. It is not in his or her words that the aphasic person is handicapped but in his or her relation to the world. Now to provide what is expected of us, we should ensure that we take charge of the aphasic person in a global way, as our professional competencies allow us to do in large part. That answer will be the only one which will allow aphasics to progress in their language, to preserve their communicative capacity and to live in better harmony with the differences between what life used to be and what it is now.

L. BLOMERT Who’s the expert? 1995, Amateur and professional judgment of aphasic communication ; Topics in Stroke Rehabilitation – vol.2, pp.64-71

Chris CODE et coll., 1999, The emotional impact of aphasia, Seminars in speech and language – vol. 20, n°1, pp.18-31