1. G. Auchmuty. “Dual variational principles for eigenvalue problems”, Proceedings of Symposia in Pure Mathematics, Vol. 45, Part 1 (1986), pp. 55–71.
2. Chew Soo Hong, Zhen Quan. “Integral global optimization”. Lecture Notes in Economics and Mathematical Systems 298 (1988).
3. F.H. Clarke. “Optimization and Nonsmooth Analysis”. J. Wiley and Sons (1983).
4. R. Correa, J.-B. Hiriart-Urruty. “A first order sufficient condition for optimality in nonsmooth optimization”. To appear in Mathematische Nachrichten
5. R. Durier. “On locally polyhedral convex functions”. In “Trends in Mathematical Optimization”, International Series of Numerical Mathematics, Birkhäuser Verlag (1988), pp. 55–66.