“…The investigations can be classified according to the anisotropy and inhomogeneity of the media under consideration. For example, Wu et al [34], Hernandez-Martinez et al [12], Wang et al [33] and Fendoğlu et al [7] had been working on problems of isotropic diffusion and homogeneous media, Yoshida and Nagaoka [35], Meenal and Eldho [19], Azis [3] (for Helmholtz type governing equation) studied problems of anisotropic diffusion but homogeneous media. Rap et al [23], Ravnik and Škerget [25,26], Li et al [18] and Pettres and Lacerda [22] considered the case of isotropic diffusion and variable coefficients (inhomogeneous media).…”