Redology (simplified Chinese: 红学 ; traditional Chinese: 紅學 ; pinyin: hóng xué ) is the academic study of Cao Xueqin's Dream of the Red Chamber,[ 2] one of the Four Great Classical Novels of China. There are numerous researchers in this field; most can be divided into four general groups: the first group are the commentators, such as Zhou Chun, Xu Fengyi, Chen Yupi, and others; the second group is the index group, which includes Wang Mengruan and Cai Yuanpei; the third group are the textual critics, including Hu Shih and Yu Pingbo; the final group are the literary critics, including Zhou Ruchang and Li Xifan.