《资治通鉴·晋纪·晋纪十九》
前燕国在龙山出现黑龙和白龙，交首戏游，丢下龙角离开。
燕有黑龙、白龙见于龙山，交首游戏，解角而去。
In the Former Yan, a black dragon and a white dragon appeared in the Longshan Mountains, they played around with their heads intertwined, and left after dropping a dragon's horn.