Byzantium and the Avars, 6the-9th Century AD : political, diplomatic and cultural relations / Georgios Kardaras. - Leiden : Koninklijke Brill n.v., 2019. - mapy, obr. - 251 s. ; 24 cm. - (East Central and Eastern Europe in the Middle Ages, 450-1450 ; Vol. 51). - ISBN 978-90-04-24838-0.