Liu , HuanZheng , Xiangcheng and Fu , Hongfei. (2022). Analysis of a Multi-Term Variable-Order Time-Fractional Diffusion Equation and Its Galerkin Finite Element Approximation.
            <i>Journal of Computational Mathematics</i>. <i>40</i> (5).
            814-834.
         doi:10.4208/jcm.2102-m2020-0211