“…Other models in two dimensions, such as the Post-Winternitz systems, could be considered as well as various Darboux deformations which provide isospectral or almost isospectral problems, which lead to exceptional Jacobi polynomial of Type I, II and III [57,58]. In addition, we may also consider the case where the angular part consists of exotic non-elementary functions, since explicit knowledge of the eigenfunctions is not readily obtainable [18,25,26].…”