Xu , Qinwu and Zheng , Zhoushun. (2014). Finite Difference/Collocation Method for Two-Dimensional Sub-Diffusion Equation with Generalized Time Fractional Derivative.
            <i>Journal of Mathematical Study</i>. <i>47</i> (2).
            173-189.
         doi:10.4208/jms.v47n2.14.03