In 1987, he was appointed to the faculty of the University of California, Berkeley; starting in 1998, he divided his time between Berkeley and the University of Leiden, until 2003, when he retired from Berkeley to take a full-time position at Leiden.
In 1987, he was appointed to the faculty of the University of California, Berkeley; starting in 1998, he split his time between Berkeley and the University of Leiden until 2003 when he retired from Berkeley to focus on his position at Leiden.