Du Yucai's dialect study paid attention to the comparison. Its materials and methods were for reference to Chinesehistory and modern Chinese dialect study.
段玉裁的方言研究注重目验和历时、共时的比较，其材料及方法可供汉语史和现代汉语方言研究参考。
2
The works related Buddhism in Du Fu's poems were the important materials of studying Du Fu's thoughts.
杜诗中与佛教有关的作品是研究杜甫思想的重要资料。杜甫对佛教的认识有一个由浅入深的过程。
3
Through checking historical materials, it points out that the descriptions about the upper course of the Yellow River in various Yuan documents all stemmed from Du Shi.