However, it is an indisputable fact that "metrical poetry" was not put forward by Guiguzi. Mature metrical poems appeared in the Tang Dynasty, which were called "new style poems" or "modern style poems" at that time, and were divided into quatrains, metrical poems and parallel poems. Its source is the "new-style poem" which appeared in Qiyong of the Southern Dynasty in the Southern and Northern Dynasties next year, and it is called "Yongming-style poem". The emergence of "Yongming Style" new poems stems from the fact that writers and linguists Shen Yue and Zhou Yong announced the rules of Chinese phonetic system, namely the "four tones" rule. The representative poets of "Yongming Style" new poetry mainly include Xie Mao, Yin Keng and He Xun. Du Fu once studied the poems of Yin Keng and He Xun.