“…A variety of such methods have been developed, and each has its own area of applicability. There exist several means to study them, for example, Wentzel-Kramers-Brillouin [1], perturbation [2], the quasilinearization method [3], the variational method [4], function analysis [5,6], the eigenvalue moment method [7], the analytical transfer matrix method [8][9][10], and numerical shooting method [11,12].…”