Anna participated actively in the Christianization of Rus: she acted as the religious adviser of Vladimir and founded a few convents and churches herself. It is not known whether she was the biological mother of any of Vladimir's children, although some scholars have pointed to evidence that she and Vladimir may have had as many as three children together.[3] French historian, Jean-Pierre Arrignon argues that Yaroslav the Wise was in fact Anna's son, as this would explain his interference in Byzantine affairs in 1043.[4] This view is corroborated by the study of Yaroslav's remains carried out in 1939–1940, which would place him amongst Vladimir's youngest children (with 986 as his estimated date of birth).[5] Furthermore, Yaroslav's maternity by Rogneda of Polotsk has been questioned since Nikolay Kostomarov in the 19th century.[6][7][8]