Remarck
I can not end this commentary without adding a brief remark. The introduction of
Gegenbauer matrix polynomials was made in Ref. [7]. In Ref. [9] the basic reference
given is [13]. However, reference [13] appeared nine years later, and several of the
formulas in [13] are incorrect. As a single example, we will consider formula (5) of
[9] (which is the same formula (13) in [13]):
F =
1 − 2xt + t
2−A = ∞
n=0
CA
n (x)t
n (5)