隋书
The Pei Shih and Book of Sui both tell that one descendant of Dongmyeong was Gutae who was sincere in his benevolence. When he first established his country in the territory of the former commandery of Daifang, the prefect of the Han territory of Liaodong, Gongsun Du, had his daughter marry [Gutae]. Afterwards [his country] became a powerful state among the Eastern Barbarians.