《资治通鉴·晋纪·晋纪九》
刘琨牙门将邢延把一块碧石献给刘琨，刘琨又送给拓跋六，拓跋六又去邢延那里索求碧石，没有得到，就抓走邢延的妻子儿女。
琨牙门将邢延以碧石献琨，琨以与六修，六修复就延求之，不得，执延妻子。
Liu Kun's subordinate Xing Yan dedicated a green gem to Liu Kun, Liu Kun gave it to Tuoba Liu, but Tuoba Liu lacked integrity and went to Xing Yan to ask more green gems; because he didn’t get it, thus kidnapped Xing Yan’s wife and children.