He directed the university 's Institute of Mathematics for most of the years from 1967 to 1996 , and was rector of the university from 1975 to 1981 .
He was an invited speaker at the International Congress of Mathematicians in 1966 .
speaker directed the university 's Institute of Mathematics for most of the years from 1967 to 1996 , and was rector of the university from 1975 to 1981 .
He was an invited speaker at the International Congress of Mathematicians in 1966 .