The history of Galician-Volhynian Ruthenia in the first half of the 14th century is very poorly sourced. A Ukrainian historian, Oleg Kupcinskij, who had strenuously collected all available clues and information about the Galicia-Volhynia documents from the 13th century and the first half of the 14th century, underto- ok to reconstruct the state of the sources that were either lost or deformed with great commitment. However, documents stored in the Metrica Regni which were included there by the heirs of the village Zablocce in 1533 and translated from Ru- thenian to Latin without chronological elements, escaped his notice. One of them, the endowment made by Duke [Boleslaw] Jerzy Trojdenowicz (together with his mother Maria Juriewna Trojdenowa) for Chodor Holowacz, provides us with new information about the beginning of the reign exercised by Boleslaw Jerzy II in the Galician-Volhynian Ruthenia. I believe that both parts of Boleslaw Jerzy II's monarchy maintained state sovereignty under the scepter of one ruler. Even tho- ugh the Masovian Piast took over the Galician-Volhynian Ruthenia being a heir of his uncles and grandfather, Wolhynia was a part of the state which had just been incorporated to Jerzy Lwowic's monarchy, i.e. about 1304, after Mscislaw II's consent. What is more, boyars' rebellions that finished with tragic deaths of the Dukes: Jerzy, Andrzej, Lew II and Boleslaw Jerzy II, took place just there.