Alexander Jagiellon
The Bychowiec chronicle used many medieval documents as its sources, primarily earlier versions of Lithuanian Chronicles, which in turn used other chronicles, including the Galician–Volhynian Chronicle. After about 1446, the chronicle became an independent source, using notes made during the reign of Alexander Jagiellon. The chronicles probably had access to notes or chronicles of Jonas Goštautas as his activities in 1440–53 are particularly detailed.