1. Hilbert’s original article
2. Geometric methods in theory for ordinary differential equations;Arnold,1983
3. On the uniqueness of the limit cycles of some nonlinear oscillation equations;Zhang;Doko Acad SSSR,1958
4. The periodic solution and limit cycles of differential equation with parameters;Chen;Acta Math Sinica,1963
5. Bifurcations of limit cycles forming compound eyes in the cubic system;Li;Chin Ann Math,1987