《辽史·本纪·卷十九》
皇上听说宋国设置关河，修治壕沟，恐怕成为边境患害，于是与南、北枢密吴国王萧孝穆、赵国王萧贯宁谋划夺取宋先前允诺割让的关南十县地域，并派萧英、刘六符出使宋国。
上闻宋设关河，治壕堑，恐为边患，与南、北枢密吴国王萧孝穆、赵国王萧贯宁谋取宋旧割关南十县地，遂遣萧英、刘六符使宋。
The emperor heard that the Song state had set up border passes and dug trenches, fearing that it would become a border threat. So he conspired with the Southern and Northern Prime Ministers, Xiao Xiaomu and Xiao Guanniang, to seize the territory of the ten counties south of the border that Song had previously promised to cede, and sent Xiao Ying and Liu Liufu to the Song state.