“Existence of Solutions and Hyers-Ulam Stability for a Coupled System of Nonlinear Langevin Equations Involving φ-Riemann-Liouville and ψ-Caputo Fractional Derivatives Subject to Mixed Boundary Conditions”. 2025. Gulf Journal of Mathematics 20 (2): 489-508. https://doi.org/10.56947/gjom.v20i2.3279.