Wahash HA, Panchal SK. Positive solutions for generalized Caputo fractional differential equations using lower and upper solutions method. J Frac Calc & Nonlinear Sys [Internet]. 2020 Dec. 30 [cited 2025 Oct. 29];1(1):1-12. Available from: https://www.sabapub.com/index.php/jfcns/article/view/78