Coupled System of (k, ψ)-Hilfer and (k, ψ)-Caputo Sequential Fractional Differential Equations with Non-Separated Boundary Conditions. - Furkan Erkan; Nuket Aykut Hamal; Sotiris K. Ntouyas; Jessada Tariboon; Phollakrit Wongsantisuk (Axioms, 2025)