《新唐书·列传·卷十六》
嗣真常说： 隋时乐府有《堂堂曲》，表明唐天子再度受命，近来有 侧堂堂，桡堂堂 的歌谣。侧，是不正的意思；桡，有危险的意思。
嗣真常曰： 隋乐府有《堂堂曲》，明唐再受命，比日有 侧堂堂，桡堂堂 之谣，侧，不正也，桡，危也。
Sizhen often said: in Sui Dynasty, the Music Bureau had a song called "堂堂曲", indicating that the Tang emperor would take office again. Recently, there is a song called "侧堂堂，桡堂堂". "侧" means improper; "桡" means dangerous.