It is my pleasant duty to give heartfelt thanks to all those who have helped me in the completion of the present work or who have made its publication possible. First, those friends and colleagues who have given me the benefit of their apt and learned council: Hassan Ansari (Princeton), Meir Bar-Asher (Jerusalem), Patricia Crone (Princeton), Fariborz Hakami (Paris), Christian Jambet (Paris), Etan Kohlberg (Jerusalem), Wilferd Madelung (Oxford), and Guy Monnot (Paris). Then the editors and managing editors who have given me their lively support: Christophe Lebbe (Editions de Brepols), Cristina Scherrer-Schaub and Gérard Colas (Journal Asiatique), Marie-Joseph Pierre and Jean-Daniel Dubois (Apocrypha), Hervé Danesi (Journal des Savants, Académie des Inscriptions et Belles Lettres), Maria Szuppe (Studia Iranica), Jean-François Colossimo (Editions du Cerf), and Guy Stavridès (CNRS Editions). Last, I thank the Persian Heritage Foundation and its president, my teacher and friend, Professor Ehsan Yarshater, for lending support for the English translation of this book, which my friend and colleague Professor Eric Ormsby has carried out. To all these I wish to express my profound gratitude.