“…The case of Jacobi polynomials may be considered as a special case of a Sturm-Liouville basis on [0, π/2]. In this situation, both the GKS and the HGP property hold [24,25,26]. Actually, it is a unique situation for orthogonal polynomials, since they are the only ones, up to a linear change of variables, for which the HGP property holds (see [18,17,19]) (under some mild extra condition on the support of the measure which represents the product formula).…”