1. Explicit imbedding of the (punctured) disc into ℂ2;Alexander;Comment. Math. Helv.,1977
2. Singularities of differentiable maps, volume of Monographs in Mathematics;Arnold,1985
3. Differential Geometry of Curves and Surfaces;Do Carmo,1976
4. Gradient-like and integrable vector fields on ℝ2;Chicone;Manuscripta mathematica,1984
5. Global Aspects of Classical Integrable Systems;Cushman,1997