He retired from Princeton in 1989 , after which he took a half - time position at the University of Rochester .
He then went to Princeton University as an Instructor , and was eventually promoted to full Professor in 1961 .
He retired from Princeton University in 1989 , after which he took a half - time position at the University of Rochester .
He then went to Princeton University as an Instructor , and was eventually promoted to full Professor in 1961 .