《新唐书·本纪·卷五·睿宗 玄宗》
景龙四年，玄宗到京都朝见君主，便被留在京城不让返回。
景龙四年，朝于京师，遂留不遣。
On the fourth year of Jinglong, Emperor Xuanzong went to the imperial capital to pay respects to his sovereign and was detained in the capital and not allowed to return.