 It is not clear why the authors of the "Primary Chronicle", who faithfully followed George Hamartolus in other details, chose to omit the very mention of Photius's efforts at Christianizing the country.In order to explain this conspicuous silence, Boris Rybakov constructed an intricate conspiracy theory, suggesting that Mstislav the Great (Grand Prince of Kiev (ruled 1125–1132) and supposedly a pro-Scandinavian and anti-Byzantine ruler) deliberately ordered the removal of the account of Askold's Christianization.Late medieval Russian sources (such as the Nikon Chronicle of the 16th century) knew of the Byzantine account of the 9th-century Christianization and attempted to reconcile it with the traditional version of Vladimir's conversion of Kiev in 992.