《北史·列传·卷二十九》
杨约知道这条计谋可行，又对杨素说： 现在，主上对皇后的话没有不听的。应该利用这个机会，早日寻找靠山，这样就可以长久地保持荣禄，传福寿给子孙。
约知其计行，复谓素曰： 今皇后之言，上无不用，宜因机会，早自结托，则匪惟长保荣禄，传祚子孙。
Yang Yue knew that the strategy was feasible and then said to Yang Su: Now, the emperor always listens to what the empress says. We should seize this opportunity and find a backer for ourselves as soon as possible. In this way, we can maintain our wealth and glory for a long time and pass on our blessings to our descendants.