Zhang, Xingqiu, Zhuyan Shao, Qiuyan Zhong, and Zengqin Zhao. “Triple Positive Solutions for Semipositone Fractional Differential Equations M-Point Boundary Value Problems With Singularities and p–q-Order Derivatives”. Nonlinear Analysis: Modelling and Control 23, no. 6 (December 20, 2018): 889–903. Accessed April 27, 2025. https://www.zurnalai.vu.lt/nonlinear-analysis/article/view/13149.