//-->
An elementary proof of the Fritz-John and Karush–Kuhn–Tucker conditions in nonlinear programming
Birbil, Ş İ, (2007)
On Classes of Generalized Convex Functions, Farkas-Type Theorems and Lagrangian Duality
Frenk, J.B.G., (1997)
Introduction to Convex and Quasiconvex Analysis
Frenk, J.B.G., (2001)