 Since then, he has been professor until his retirement in 1994, then professor emeritus at the Université de Paris-Sud in Orsay.He was a Plenary Speaker at the International Congress of Mathematicians in 1962 in Stockholm and an Invited Speaker at the 1986 ICM meeting in Berkeley, California.He was elected corresponding member of the French Academy of Sciences in 1982 and full member in 1998.