R. Sahandi Torogh, Tran., “Existence of Positive Solutions for (p1,p2) Laplacian System to Dirichlet Boundary Conditions”, Int.J. Fundam. Phys. Sci, vol. 6, no. 4, pp. 17–22, Dec. 2016, doi: 10.14331/ijfps.2016.330098.