“A Two-Level Factored Crank-Nicolson Method for Two-Dimensional Nonstationary Advection-Diffusion Equation with Time Dependent Dispersion Coefficients and Source Terms”, Adv. Appl. Math. Mech., vol. 13, no. 5, pp. 1005–1026, June 2021, doi: 10.4208/aamm.OA-2020-0206.