Siegmund (Sigismund) Freiherr von Herberstein ( ) diplomat, writer, historian and member of the Holy Roman Empire Imperial Council. He was twice in Muscovy: 1517, 1526. Issues: Problem of origin of east Slavs; Establishment of Russian state system; Norman and Slavonic conceptions of Kiev Rus establishment; Social and political system of Old Russian state; Christianization of Kiev Rus. Problem of origin of east Slavs Slavs First mentioned in VI AD ( Procopius of Caesarea ) Etymology : Slav