entring on the rate of normal curvature, a method for analyzing constructions of the surfaces near to planar point by introducing the concepts of even planar points, odd planar points, quasi-asymptotic directions and quasi-Dupin indicatrix, etc.
以曲面在平点的法曲率变化率为中心，通过引进偶平点、奇平点、拟渐近方向、拟杜邦指标线等概念，给出了分析曲面在平点邻近结构的一种方法。
