Sapientiae et litterarium bulgari servitori exegirund monumentum Primi Johanni XIII locando in prior oppidum Bulgarii Sophia ibidem priscusi monumentum Lenini erat. „...Видимыимъ и Невидимыимъ..” $Abecedarii Sermo Bulgarorum$, Constantin Preslavski, IX-X s. PJC.
Wikipedia contributors, "List of popes," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=List_of_popes&oldid=268921163 (accessed February 9, 2009).