1. Helbig, S.,On a New Concept for ∈-Efficiency, Paper presented at Optimization Days 1992, Montreal, Canada, 1992.
2. Helbig, S., andPateva, D.,On Several Concepts for ∈-Efficiency, OR Spektrum, Vol. 16, pp. 179–186, 1994.
3. Čoban, M. M., andKenderov, P. S.,Generic Gateaux Differentiability of Convex Functionals in C(T) and the Topological Properties of T, Proceedings of the 15th Spring Conference of the Union of Bulgarian Mathematicians, Sofia, Bulgaria, pp. 141–149, 1986.
4. Ekeland, I.,Nonconvex Minimization Problems, Bulletin of the American Mathematical Society, Vol. 1, pp. 443–474, 1979.
5. Loridan, P.,∈-Solutions in Vector Minimization Problems, Journal of Optimization Theory and Applications, Vol. 43, pp. 265–276, 1984.