1. Singularities of Smooth Mappings;Arnol'd;Russ. Math. Surv.,1968
2. Singular Points of Functional Equations;Bartle;Trans. Am. Math. Soc.,1953
3. On Nonlinear Perturbations of the Eigenvalues of a Compact Selfadjoint Operator;Berger;Bull. Am. Math. Soc.,1967
4. Nonlinear Eigenvalue Problems and Group Invariance;Browder,1970
5. Some Mappings with Topological Degree Zero;Cronin;Proc. Am. Math. Soc.,1956