Fengxia Zheng and  Chuanyun Gu,  A Sum Operator Method for Unique Positive Solution to a Class of Boundary Value Problem of Nonlinear Fractional Differential Equation.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    November 2015, vol. 104(8). 509 - 512
    [viewed 23 April 2024]. Available from: https://publications.waset.org/pdf/10003199.