History of the Northern Dynasties: He reached Zhangye, met the King of Gaochang, then received lands of the Western Regions and set up four…
He reached Zhangye, met the King of Gaochang, then received lands of the Western Regions and set up four commanderies, including Xihai.
丙午，次張掖
Location: 北史 卷12 大業5年
Four commanderies were established: Xihai, Heyuan, Shanshan and Qiemo.
置西海、河源、鄯善、且末等四郡
Location: 隋書 卷003 帝紀 大業5年6月
Place: 張掖
Show on the map — open History of the Northern Dynasties (Beishi), Annals