Hypatian Codex
The Hypatian Codex, also known as Hypatian Letopis or Ipatiev Letopis, is a compendium of three Rus' chronicles: the Primary Chronicle, Kievan Chronicle and Galician–Volhynian Chronicle. It is the most important source of historical data about Kievan Rus'. The language of this work is Old Church Slavonic with many East Slavisms.