1. R. Courant and D. Hilbert, Methods of mathematical physics, vol. 1, New York, 1953.
2. On the numerical integration of ∂²𝑢/∂𝑥²+∂²𝑢/∂𝑦²=∂𝑢/∂𝑡 by implicit methods;Douglas, Jim, Jr.;J. Soc. Indust. Appl. Math.,1955
3. On the numerical integration of quasilinear parabolic differential equations;Douglas, Jim, Jr.;Pacific J. Math.,1956
4. The solution of the diffusion equation by a high order correct difference equation;Douglas, Jim, Jr.;J. Math. and Phys.,1956
5. On the relation between stability and convergence in the numerical solution of linear parabolic and hyperbolic differential equations;Douglas, Jim, Jr.;J. Soc. Indust. Appl. Math.,1956