- 1979-80 J.E. Procter Fellow, Princeton University.
- 1980-83 Attaché de Recherche, Centre National de la Recherche Scientifique and Université de Paris-Sud (Orsay).
- 1983-86 Chargé de Recherche, Centre National de la Recherche Scientifique and Université de Paris-Sud (Orsay).
- 1986-87 Assistant Professor of Mathematics, University of Southern California.
- 1987-89 Associate Professor of Mathematics, University of Southern California.
- 1989 – 2021 Professor of Mathematics, University of Southern California.
- 2022 – Professor of Mathematics Emeritus, University of Southern California.
- 2022 – Adjunct Professor of Mathematics, Michigan State University.