“…a special case of Gelfand hypergeometric function [2,4], was known to, among others, the Japanese authors Mizukawa and Tanaka [15], who used them to prove their orthogonality in some special cases. Later, Mizukawa [13] gave a complete orthogonality proof of (1.9) using Gelfand pairs, then [15] used character algebras and closely following this proof came Iliev and Terwilliger's proofs, first for n = 2 [11], then for general n in [12], in which they used tools from Lie algebra theory. In these proofs the authors found it convenient to use 1−u ij instead of u ij as parameters in (1.9), and also to use…”