Hiriart-Urruty, On Optimality Conditions in
Nondifferentiable Programming, Math.
Yang: On second-order symmetric duality in nondifferentiable programming, J.
Beldiman: Higher-order duality for a nondifferentiable programming problem, Internat.
Hiriart-Urruty, "On optimality conditions in
nondifferentiable programming," Mathematical Programming, vol.
But the corresponding conclusions cannot be obtained in
nondifferentiable programming with the aid of invexity because of the existence of requiring a derivative in the definition of invexity.
Hiriart-Urruty: Refinements of necessary optimality conditions in nondifferentiable programming I, Appl.
Jourani: Constraint qualifications and Lagrange multipliers in nondifferentiable programming problems, J.