1. Singularities of Differentiable Maps, vol. I;Arnolʼd,1986
2. Singularities of Caustics and Wave Fronts;Arnolʼd,1990
3. The unfolding and determinacy theorems for subgroups of A and K;Damon;Mem. Amer. Math. Soc.,1984
4. The theory of caustics and wave front singularities with physical applications;Ehlers;J. Math. Phys.,2000
5. Lagrangian and Legendrian singularities;Goryunov,2007