Alain Ducellier (1934), professor of the history of the Byzantine and Balkan history of the University of Tuluz Le Mirail. The main object of his studies is especially the Byzantine ideology and thinking, as well as the relations of the Byzantine Empire with the neighbors. He is the author and co-author of more than forty works. Michel Balard (1936), Emeritus professor at Paris I University, chairman of the Association of History and Archeology of Sucy-en-Brie and of the Association of History and Archeology Associations in Paris and Île-de-France. He devotes his teaching and research to the political and economic relations between East and West in the Middle Ages. He has run a research group at CNRS for western colonization in the Mediterranean during the Middle Ages.