Complex sentence: In 1966-67 he was again a guest lecturer, this time in Mainz, Leipzig, Rostock and Greifswald.In 1980 he was a short time guest lecturer in Fort Wayne, Ill. He was professor of Christian history (1969--1987) at Lund.
Split into simpler sentences: In 1966-67 he was again a guest lecturer, this time in Mainz, Leipzig, Rostock and Greifswald. Returning to Sweden, he was professor of Christian history (1969--1987) at Lund.