Hu Z, Liu W. Solvability of a Coupled System of Fractional Differential Equations with Periodic Boundary Conditions at Resonance. Ukr. Mat. Zhurn. [Internet]. 2013Nov.25 [cited 2024Nov.23];65(11):1463–1475. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/2526