sentences:  His previous tours in Moscow were as Vice Consul and Third Secretary (1961–1963), Minister Counsellor and Deputy Chief of Mission (1974–1978), and Chargé d'Affaires "ad interim" (1981).After he retired from the Foreign Service in 1991, Matlock reentered the academic world, becoming the Kathryn and Shelby Cullom Davis Professor of the Practice of International Diplomacy at Columbia.After five years in that position he moved to the Institute for Advanced Study in Princeton, New Jersey, where he was George F. Kennan Professor from 1996 to 2001.