He subsequently wrote a paper about integration problems of Italian guest workers in Switzerland.
He became a lecturer in 1966 and was an ordinary professor of social and economic history at the Free University of Berlin from 1968 to 1971.
From 1971 to 1995, he was an ordinary professor of general and Swiss modern history at the University of Zurich.
He was one of the pioneering social historians of German-speaking Switzerland alongside Markus Mattmüller (Basel) and Erich Gruner [de] (Bern).
He co-organised the first seminar for women's history at the University of Zurich with his assistant Jakob Tanner.