Among the most valuable sources of information to which Friar William had access was the narrative by Benedict of Poland of his journey to the Court of Kuyuk Khan in 1246 in company with John of Pian de Carpine. It is highly probable that Friar William met Friar John before leaving France in 1248 and received advice from him and possibly communication of his report to the Pope if it was written at that time. At all events as the route followed by the latter was for much of the way through the same countries traversed by Friar William and as the two narratives complete and corroborate each other it has been deemed advisable to give' in full the relations of Friars John and Benedict. As to the first part of the Historia Mongalorum of Friar John relating to the customs and history of the Mongols I have introduced in foot-notes to the text all such portions of it as bear directly on the narrative of Friar William ; and similar use has been made of the account of the mission of Friar Ascelin in 1247 which has reached us in the extracts preserved by Vincent of Beauvais of the report made by Simon of St. Quentin a member of the mission.