Ⅱ.微分方程組 嘉当在微分方程組理論方面的主要文章是[1]。讀者可以在嘉当的书[9]中找到Pfaff組理論的很清楚的闡述。一个Pfaff組是包括一定数目的具有形状A_1dx_1++A_2dx_2+…+A_ndx_n的方程組,其中A_1,…,A_n是x_1,…,x_n的函数,方程組中还可能包括一些形状为F(x_1,…,x_n)=0的方程。一个由x_i=f_i(t_1,…,t_r) II. Differential Equation Groups Jiadang’s main article in the theory of differential equations is [1]. The reader can find a clear explanation of the theory of the Pfaff group in Jiadang’s book [9]. A Pfaff group consists of a certain number of equations with shapes A_1dx_1++A_2dx_2+... +A_ndx_n, where A_1,...,A_n are functions of x_1,...,x_n, and the equations may also include some shapes for F(x_1,... ,x_n)=0 equation. One by x_i=f_i(t_1,...,t_r)