Sources

1) Source: The Russian Primary Chronicle "But Olga was in Kiev with her son, the boy Svyatoslav.". Reference: 6452 (944) (Data from secondary evidence)
2) Source: The Russian Primary Chronicle "Svyatoslav replied that they had need of a prince, but Yaropolk and Oleg both refused, so that Dobrynya suggested that the post should be offered to Vladimir. For Vladimir was son of Malusha, stewardess of Olga and sister of Dobrynya. Their father was Malk of Lyubech, and Dobrynya was thus Vladimir's uncle.". Reference: 6478 (970) (Data from secondary evidence)