Proceedings of a meeting held in Luminy, France, Sept. 1989. Three of the 17 papers are in French (without English abstracts). We are pleased to note that 85% of these mathematicians recognize the importance of writing in the world's scientific language (the great sci-tech house Dunod has just announced it will commence English language publishing, joining VCH, de Gruyter, the Kluwer group, and the leader, Springer Verlag). Annotation copyright Book News, Inc. Portland, Or.