The Burislav reference article from the English Wikipedia on 24-Apr-2004
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Burislav

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Burislav, Burisleif, Burysław is the name of mythical Wendish king from Scandinavian sagas who is said to rule over Wendland. He is said to be father of Gunhilda and maybe also Sigrid the Haughty. There are three possible hypothesis over his identity: first, that there actually was Slavic prince of that name; second, that this was name given by saga authors to any Slavic prince; third, that he is a compound person, combining two Polish rulers: Mieszko I of Poland and Boleslaus I of Poland.