Caliphate and kingship : Amir Hasan Siddiqi. in medieval Persia / Siddiqi, Amir Hasan. Abbasids. DS288 .S5 955 AMC "The subject treated in this book was presented as a thesis ... at the London university in 1934."--Introd. "Bibliographical list of authorities": p. [177]-181. Philadelphia : Porcupine, c1977. c1977. 1977 Text xi, 120 p. ; eng Iran History 640-