Education: Universities of Leiden and Utrecht, Mathematics and Physics, 1940--49 (with war-time interruptions) Ph.D. in Mathematics, Leiden, 1949 Regular professorships (Mathematics) Technical University Delft (Netherlands), 1951-(Jan)1953 University of Wisconsin (Madison), (Feb)1953--64 (Chairman, Program in Applied Mathematics and Engineering Physics, 1956--61) University of California San Diego (La Jolla), 1964--74 (Chairman, Dept of Mathematics, 1971--73) University of Amsterdam, 1974--(Jan)93 (Director, Math. Institute, 1980--83)