《北史·本记·卷八》
御马圈地上铺设毡垫，吃的有十多种东西，交配时特地建造青庐，安排丰盛食物，皇帝亲临观看。
御马则藉以氈罽，食物有十余种。将合牝牡，则设青庐，具牢馔而亲观之。
The emperor's horse paddocks were covered with felt and the horses were fed more than ten kinds of food. Special blue tents were built and lavish food was prepared for their matings, which the emperor personally observed.