Eq. (106View Equation) has been obtained using a not so well known mathematical relation between the Legendre functions and polynomials:
1 integral 1 dzP (z) - V~ ------2---l2------2-----= Ql(x)Pl(y) 2 -1 (xy - z) - (x - 1)(y - 1)
(where 1 < y < x is assumed). See Appendix A in Ref. [10Jump To The Next Citation Point] for the proof. This relation constitutes a generalization of the Neumann formula (see footnote after Eq. (103View Equation)).