Tritton, A. S.  1881-1973 <br/><br/>
The caliphs and their non-muslim subjects :  a critical study of the covenant of'Umar / 
by A. S. Tritton 
 - London :  Frank Cass,  1970 
 - 240 p. ;  22 cm. 
<br/><br/>Includes index 
<br/><br/><label>ISBN: </label>0714619965 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Caliphate
<br/><br/><label>Subjects--Geographic Terms: </label><br/>Islamic Empire--History