1. Calculus of Variations and Partial Differential Equations of First Order, Part I. Partial Differential Equations of the First Order;Carathéodory,1965
2. Singularities of envelopes of families of submanifolds in RN;Carneiro;Ann. Scient. Ec. Norm. Sup,1983
3. Solution de plusieurs problems;Clairaut,1734
4. Methods of Mathematical Physics I, II;Courant,1962