However, in the literature after Yuan Dynasty, including poetry, some scholars only fill in the metrical form of poetry according to the rhyme and even words of ancient books. During the Song and Yuan Dynasties, due to the problems of foreigners, the phonetic changes were very different. In Qing Dynasty, local phonetics became the object of research and textual research on the phonology of Tang and Song Dynasties. Wang Niansun and his son in Gaoyou, as well as Gu's Rizhilu, can know that their mastery of "primary school" (writing, exegesis and phonology) is related to their failure to give up reading dialect pronunciation. Reading can not but pay attention to words, phonology and exegesis. Of course, dialect is the most effective language even closer to the written form of ancient books. Especially in the Four Books and Five Classics, Tang Poetry and Song Poetry, there are styles of paying attention to trivial matters, chewing words and judging words, so we must listen to the voice of dialects. The vernacular is a little more open.