1. Differentiable Germs and Catastrophes;Bröcker,1975
2. Stable mappings and their singularities;Golubitsky,1973
3. Differential Topology;Hirsch,1976
4. A. Andronov, E. Leontovich, I. Gordon, A. Maier Theory of bifurcations of dynamical systems on a plane Israel Program for Sci. Trans., 1971.