Complex sentence: In 1939 he was elected assistant professor and, later, professor in University of Thessaloniki and in 1954 was elected professor of civil law in University of Athens holding this position until 1974, when he retired.
Split into simpler sentences: In 1939 he was elected assistant professor and, later, full professor in University of Thessaloniki. In 1954 he was elected professor of civil law in University of Athens, holding this position until 1974, when he retired.