O175
This paper uses the Poincare-Bendixson's annular region theorem with existenceof limit cycles of a cfass of nonlinear differential equation.
张谋.关于微分方程X=ψ(y)-F(x,y)Y=h(y)-g(x)极限环的存在性[J].土木与环境工程学报(中英文),1994,16(1):