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(ئینگلیزی) (27 June 2019) The Eastern Frontier: Limits of Empire in Late Antique and Early Medieval Central Asia، Bloomsbury Publishing، p. 65 ISBN: 978-1-78831-722-1. ""The collapse of the Hephthalite domains made neighbours of the Türk Khāqānate and the Sasanian Empire, both sharing a border that ran the length of the River Oxus. Further Turkish expansion to the west and around the Caspian Sea saw them dominate the western steppes and its people and extend this frontier down to the Caucasus where they also shared a border with the Sasanians. Khusrow is noted at the time for improving the fortifications on either side of the Caspian, Bāb al-Abwāb at Derbent and the Great Wall of Gorgān.""

(ئینگلیزی) (26 January 2011) Central Asia in World History.، Oxford University Press، p. 49 ISBN: 0199793174. ""The Türks created the First Central Asian transcontinental empire from Manchuria to the Black Sea.""

Ktrinko