[1] H. B. Cui, Auto CAD R14 practical course in Chinese version(In Chinese), People’s Post & Telecom Publishing House, Beijing, pp.97-132, 1988
[2] Y. J. He, Computer graphics calculation and practice(In Chinese), Hunan Technology Publishing House, pp.116-157, 1990
[3] Y. X. Xu, Geometry base for computer aided design and manufacture(In Chinese), Jiangsu Technology Publishing House, Nanjing, pp.6-15, 1996