Hypatian Codex
The Hypatian Codex (also known as Hypatian Letopis or Ipatiev Letopis, Cyrillic "Ипатьевская летопись") is a "svod" (compendium) of three "letopis" chronicles: the "Primary Chronicle", "Kievan Chronicle" and "Galician-Volhynian Chronicle". It is the most important source of historical data for southern Rus'.