Photius I Saint, Patriarch of Constantinople ca. 820-ca. 891.
The Patriarch and the Prince: the letter of Patriarch Photios of Constantinople to Khan Boris of Bulgaria /
[edited] by Despina Stratoudaki White, Joseph R. Berrigan 
. - Brookline  : Holy Cross Orthodox Press,  1982 
. - 102 p.  22 cm. 
 - (Archbishop Iakovos library of ecclesiastical and historical sources  ; no. 6 )
<br/>К.: Бібліогр. : с. 91-95 
<br/><label>  ISBN: </label>0-916-586-52-9