On some nonsmooth equilibrium constrained minimization models using epiderivative Bhuwan Chandra Joshi, Murari Kumar Roy, Savin Treanţă and Cristina-Mihaela Cebuc RAIRO-Oper. Res., 59 3 (2025) 1665-1680 Published online: 20 June 2025 DOI: 10.1051/ro/2025062