Stephenson, Paul.
Byzantium’s Balkan frontier: a political study of the Northern Balkans, 900-1204 /
Paul Stephenson 
. - Cambridge : Cambridge University Press,  2000 
. - xii, 352 p.  map.  24 cm. 
<br/>К.: Бібліогр. : c. 324-344, Index 
<br/><label>  ISBN: </label>0-521-77017-3