Ewers of this type are based on bronze prototypes, such as the ewer illustrated in Gems of China's Cultural Relics, 1993, pl. 82. See, also, the similar proto-porcelain ewer in the Ashmolean Museum illustrated by W. Watson, Pre-Tang Ceramics of China, London, 1991, pl. V; and another in Zhongguo meishu quanji; Gongyi meishu bian; Taoci (The Great Treasury of Chinese Fine Arts; Arts and Crafts; Ceramics), Shanghai, vol. 1, 1991, p. 76, no. 89.