《辽史·本纪·卷二十八》
皇上派驸马萧昱领兵前往广平淀保护后妃，派行宫小底乙信带着书信飞驰告知魏国王。
上遣驸马萧昱领兵诣广平淀护后妃，行宫小底乙信持书驰报魏国王。
The Emperor sent the Imperial Son-in-law Xiao Yu to lead soldiers to Guangpingdian to protect the imperial concubines and sent Yi Xin, a small official from the temporary palace, to rush to inform the King of Wei with a letter.