Analysis of information sources in references of the Wikipedia article "Protectorate General to Pacify the West" in English language version.
則天臨朝，長壽元年，武威軍總管王孝傑、阿史那忠節大破吐蕃，克復龜茲、于闐等四鎮，自此復於龜茲置安西都護府，用漢兵三萬人以鎮之。[In the first year of the Changshou era [692], under the reign of Zetian, Area Commander Wang Xiaojie of Wuwei Army and Ashina Zhongjie dealt a great blow to the Tibetans. Quici, Yutian, and the four garrisons were restored. From then on the Anxi Protectorate was restored to Qiuci with 30,000 Han soldiers.]
上元元年，河西軍鎮多為吐蕃所陷。有舊將李元忠守北庭，郭昕守安西府，二鎮與沙陀、回鶻相依，吐蕃久攻之不下。[In the first year of the Shangyuan era [760], the Hexi Army Defense Command fell to the Tibetans. Beiting and Anxi were guarded by Li Yuanzhong and the old general Guo Xin, who along with the Shatuo and Uyghurs, were able to prevent the Tibetans from taking the two garrisons.]
建中元年，元忠、昕遣使間道奏事，德宗嘉之，以元忠為北庭都護，昕為安西都護。[In the first year of the Jianzhong era [780], Yuanzhong and Xin dispatched envoys through a remote path to memorialize the emperor. Dezong commended them and Yuanzhong became protector-general of Beiting while Xin became protector-general of Anxi.]
