《周书·本纪·卷六》
而娶妻买妾，有聘纳母亲家族的，虽然说是不同宗，但仍然混杂。
而娶妻买妾，有纳母氏之族，虽曰异宗，犹为混杂。
And those who take wives and buy concubines, some hire the mother's family, although they are said to be not of the same clan, they are still mixed up.