Zhang Yan (1248~132) has always been the first to study the tune music of Ci, and his book Etymology gives a comprehensive account of the tune characteristics of Ci in Song Dynasty, which has become a valuable research material. Since then, Shen Kuo's Notes on Mengxi, Wang Zhuo's Tales of Biji Manzhi, and Zhao Delin's Records of Waiting for a Shark have all left important information.