1. J.-P. Aubin, “Contingent derivatives of set-valued maps and existence of solutions to nonlinear inclusions and differential inclusions,” in: L. Nachbin, ed.,Mathematical Analysis and Applications, Part A, Advances in Mathematics, Vol. 7A (Academic Press, New York, 1981) pp. 159–229.
2. M.S. Bazaraa, J.J. Goode and Z. Nashed, “On the cones of tangents with applications to mathematical programming,”Journal of Optimization Theory and Applications 13 (1974) 389–426.
3. M.S. Bazaraa and C.M. Shetty,Nonlinear Programming: Theory and Algorithms (Wiley, New York, 1979).
4. J.M. Borwein and H.M. Strojwas, “Directionally Lipschitzian mappings on Baire spaces,”Canadian Journal of Mathematics 36 (1984) 95–130.
5. F.H. Clarke,Optimization and Nonsmooth Analysis (Wiley, New York, 1983).