Abd-Elkawy, M. A., and R. T. Alqahtani. “Space-Time Spectral Collocation Algorithm for the Variable-Order Galilei Invariant Advection Diffusion Equations With a Nonlinear Source Term”. Mathematical Modelling and Analysis, vol. 22, no. 1, Jan. 2017, pp. 1-20, doi:10.3846/13926292.2017.1258014.