Malaterra wrote Latin history, the "De Rebus Gestis Rogerii Calabriae et Siciliae Comitis et Roberti Guiscardi Ducis fratris eius," which chronicles the history of the Normans in Italy, particularly the brothers Robert Guiscard and Roger I of Sicily, and their conquest of Sicily. Geoffrey reports Pope Urban II's bull of 5 July 1098, which made Roger and his heirs legates of the Latin church, but not much after that. Additionally, he notes Bohemond's joining the First Crusade, but not the Fall of Jerusalem or Bohemond's conquest of Antioch. These details indicate that he probably finished his history around this time in 1098. Malaterra's work is one of the three surviving contemporaneous histories of the Norman conquest of Italy, the others being those of William of Apulia and Amatus of Montecassino. Malaterra's is significant because it is the only history to significantly cover the conquest of Sicily. It seems likely that Geoffrey was writing at the behest of Roger, who was an old man by this time and may have been looking to legitimize the claims of his heirs. Unlike other medieval historians, such as Dudo of Saint-Quentin, Malaterra does not directly identify his sources, and alludes briefly to a number of informants, or "relatoribus". These may have included Roger I of Sicily, himself.