The reason is that Heine theorem is not the focus of Wu Zhongxiang's mathematical research. Wu Zhongxiang is a famous mathematician in China. Heine's theorem is not mentioned in many of his works. Heine theorem is not the focus of Wu Zhongxiang's mathematical research. Wu Zhongxiang's mathematical research direction is mainly in the fields of algebra and geometry, such as modular surface and its application, three-dimensional algebraic geometry and so on. His works on algebra and geometry will not involve Heine's theorem. Heine theorem is mainly used to derive Euler formula.