* {{citationcite web| last1=Николова |first1= В |last2=Куманов |first2= М | title=България. Кратък исторически справочник | volume= Т. 3 | place= София | year= 1983}}
* {{citationcite web| last= Kazhdan | first = Alexander | title = Rus'-Byzantine Princely Marriages in the Eleventh and Twelfth Centuries| series = Harvard Ukrainian Studies |volume =Vol. 12/13, Proceedings of the International Congress Commemorating the Millennium of Christianity in Rus'-Ukraine (1988/1989) | jstor = 41036324 | pages = 414 – 429 | publisher = Harvard Ukrainian Institute}}