Wolski, Jan Mikołaj (5 February 2019). "The Portrayal of Peter in Modern Historiography". The Bulgarian State in 927-969 : the epoch of Tsar Peter I. Leszka, Mirosław J.,, Marinow, Kirił,, Genova, Lyubomira,, Majer, Marke,, Mękarski, Artur,, Zytka, Michal (First ed.). [Łodź, Poland]. ISBN978-8323345459. OCLC1078891613.{{cite book}}: CS1 maint: location missing publisher (link)
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Wolski, Jan Mikołaj (5 February 2019). "The Portrayal of Peter in Modern Historiography". The Bulgarian State in 927-969 : the epoch of Tsar Peter I. Leszka, Mirosław J.,, Marinow, Kirił,, Genova, Lyubomira,, Majer, Marke,, Mękarski, Artur,, Zytka, Michal (First ed.). [Łodź, Poland]. ISBN978-8323345459. OCLC1078891613.{{cite book}}: CS1 maint: location missing publisher (link)