Dodgeon, Michael H.; Greatrex, Geoffrey; Lieu, Samuel N. C. The Roman Eastern Frontier and the Persian Wars: AD 363-630: a Narrative Sourcebook. Routledge. 2002. ISBN 978-0415146876.
Ekonomou, Andrew J. Byzantine Rome and the Greek Popes: Eastern Influences on Rome and the Papacy from Gregory the Great to Zacharias, AD 590–752. Rowman & Littlefield. 2008. ISBN 978-0739119778.
Hupchick, Dennis P. The Bulgarian-Byzantine Wars for Early Medieval Balkan Hegemony: Silver-Lined Skulls and Blinded Armies. Springer. 2017. ISBN 9783319562063.
Petersen, Leif Inge Ree. Siege Warfare and Military Organization in the Successor States (400-800 AD) Byzantium, the West and Islam. BRILL. 2013. ISBN 9789004254466.
Pohl, Walter. The Avars: a Steppe People in Central Europe, 567-822 AD. Beck. 2002. ISBN 9783406489693(德语).