John Tolan is professor of history at the Universite de Nantes. His books include "Saracens" and "Saint Francis and the Sultan". Gilles Veinstein is professor of history at the College de France. His books include "Merchants in the Ottoman Empire". Henry Laurens is professor of history at the College de France. He is the author of "L'empire et ses ennemis: La question imperiale dans l'histoire".