Integral invariants of a generalized Birkhoff system
广义Birkhoff系统的积分不变量

Integral invariants of a generalized Birkhoff system are studied in this paper. The condition under which the integral invariants exist in the system is given. A linear integral invariant, a universal integral invariant and an absolute integral invariant of second order of the system are obtained under the given condition. An example is given to illustrate the application of the result.