“…In addition, we note that, apart from the factors (−1) m √ π or (−1) n √ π , functions of the type R m,n (r ) have been considered in [6], where what we may consider the h → ∞ limit of the sum (4.39), namely s m (r, r ; t) = ∞ l=−m t l R m,m+l (r )R m,m+l (r ), (5.14) was proved to have the closed form expression…”