O. Balzer concluded that Vratislaus II's coronation took place on 15 June 1086, following the reports of Cosmas of Prague. O. Balzer: Genealogia Piastów, p. 108. W. Mischke, like many other medievalists, pointed that the coronation of Vratislaus II was on 15 June 1085. W. Mischke: Polska korona królów czeskich (in Polish) [retrieved 30 July 2014], p. 11–12, 27–29.
The reports of Cosmas of Prague about the coronation of Vratislaus II as King of Poland are disputed by many historians. Medievalists consider this a mistake of the chronicler. See G. Labuda: Korona i infuła. Od monarchii do poliarchii, p. 13. A detailed argument who favored Vratislaus II's coronation is presented by W. Mischke. See W. Mischke: Polska korona królów czeskich (in Polish) [retrieved 30 July 2014], pp. 11–29. M. Spórna and P. Wierzbicki believes that the reports of Cosmas are authentic. The title of King of Poland was probably received from the Emperor, who claimed feudal sovereignty over this country. M. Spórna, P. Wierzbicki: Słownik władców Polski i pretendentów do tronu polskiego, p. 496.
