From 1939 to 1970 he taught Byzantine and Modern Greek History in the University of Athens (among his students there were Angeliki Laiou, Nikolaos Oikonomides and Chryssa Maltezou), while in 1937–1946 he directed the Greek State Archives.
Dari tahun 1939 hingga 1970 ia mengajar Bizantium dan Sejarah Yunani Modern di Universitas Athena (di antara murid-muridnya ada Angeliki Laiou dan Nikolaos Oikonomidis), sementara pada tahun 1937-1946 ia memimpin Arsip Negara Yunani.