At a guess, he's referring to the Primary Chronicle, or at least the
Hypatian Codex, which contains a copy of the Primary Chronicle (dating
from ~900 CE to ~1117 CE), as well as the Kievan Chronicle (up to
~1200 CE), and the Galitsko-Volynskij Chronicle (through the 13th
Century). A possible alternative is the Laurentian Codex, which
starts with the Chronicle, then goes through the Suzdal Chronicles,
into the 15th Century.
Either set can be found online in the Krotov Library, but you may need
to brush up on your Russian, if not your Church Slavonic.
URL for the Hypatian Codex is:
And for the Laurentian:
Hope this helps... Good luck! Let us know what you find out!
Barony of Lochmere, Atlantian Kingdom