The difference between Xu and Ni

Xu was one of the masters and founders of Dou Shu in Song Dynasty. His research and practice laid the foundation for the development of Wei Zi's Dou Shu.

Ni is a master of Doushu in Ming Dynasty, and has made important contributions to the research and development of Doushu. His interpretation and understanding of Wei Zi Dou Shu has been widely recognized and used by later generations.