On the Regular Points of Zygmund Differentiable Maps
Zygmund微分映射的正则点

The main result of this article is: For any Zygmund class $C^{p,Z}$map $f:R^{n}\rightarrow R^{m}$ if $\frac{n-m}{2}\leq p\leq n-m-1$, then either mes$K_{f}>0$ or mes$C_{f}>0$. It provides a partial answer of the Hirsch Problem.