Large encyclopedias were also produced in China through the ages. The "Yiwen Leiju" encyclopedia was completed by Ouyang Xun in 624 during the Tang Dynasty, with aid from scholars Linghu Defen and Chen Shuda. During the Song Dynasty, the compilation of the Four Great Books of Song (10th century – 11th century), begun by Li Fang and completed by Cefu Yuangui, represented a massive undertaking of written material covering a wide range of different subjects. This included the "Taiping Guangji" (978), the "Taiping Yulan" (983), the "Wenyuan Yinghua" (986), and the "Cefu Yuangui" (1013). Although these Song Dynasty Chinese encyclopedias featured millions of written Chinese characters each, their aggregate size paled in comparison to the later "Yongle Encyclopedia" (1408) of the Ming Dynasty, which contained a total of 50 million Chinese characters. Even this size was trumped by later Qing Dynasty encyclopedias, such as the printed "Gujin Tushu Jicheng" (1726), which featured over 100 million written Chinese characters in over 800,000 pages, printed in 60 different copies using copper-metal Chinese movable type printing. Other great encyclopedic writers include the polymath scientist Shen Kuo (1031–1095) and his "Dream Pool Essays", the agronomist and inventor Wang Zhen (fl. 1290–1333) and his "Nongshu", and the minor scholar-official Song Yingxing (1587–1666) and his "Tiangong Kaiwu".