"Jaxa of Köpenick (sometimes Jaksa or Jacza of Copnic, Polish: Jaksa z Kopnika or Jaksa z Kopanicy, Jaksa being an early Sorbian and/or Polish form of James) (fl. 1151-1157) was a prince of the West Slavic Sprevan Duchy of Kopanica. He was an opponent of Albert the Bear during the formation of Brandenburg in 1157." - (en.wikipedia.org 31.01.2020)
