Complex sentence: From 1998 to 2001 Cohen worked as the Vice dean of Columbia University's School of International and Public Affairs, and from 1985 to 1998 he was the Director of Columbia's Graduate Program in Public Policy and Administration.
Split into simpler sentences: From 1998 to 2001 Cohen was Vice dean of Columbia University's School of International and Public Affairs. From 1985 to 1998 he was the Director of Columbia's Graduate Program in Public Policy and Administration.