1. CJM 1998 (vol 50 pp. 193)
 Xu, Yuan

Intertwining operator and $h$harmonics associated with reflection groups
We study the intertwining operator and $h$harmonics in
Dunkl's theory on $h$harmonics associated with reflection groups. Based
on a biorthogonality between the ordinary harmonics and the action of the
intertwining operator $V$ on the harmonics, the main result provides a
method to compute the action of the intertwining operator $V$ on polynomials
and to construct an orthonormal basis for the space of $h$harmonics.
Keywords:$h$harmonics, intertwining operator, reflection group Categories:33C50, 33C45 

2. CJM 1997 (vol 49 pp. 373)
 Stokman, Jasper V.; Koornwinder, Tom H.

Limit transitions for BC type multivariable orthogonal polynomials
Limit transitions will be derived between the five parameter
family of AskeyWilson polynomials, the four parameter family of
big $q$Jacobi polynomials and the three parameter family of little
$q$Jacobi polynomials in $n$ variables associated with root system $\BC$.
These limit transitions generalize the known hierarchy structure between
these families in the one variable case. Furthermore it will be proved
that these three families are $q$analogues of the three parameter
family of $\BC$ type Jacobi polynomials in $n$ variables. The limit
transitions will be derived by taking limits of $q$difference operators
which have these polynomials as eigenfunctions.
Categories:33D45, 33C50 

3. CJM 1997 (vol 49 pp. 175)
 Xu, Yuan

Orthogonal Polynomials for a Family of Product Weight Functions on the Spheres
Based on the theory of spherical harmonics for measures invariant
under a finite reflection group developed by Dunkl recently, we study
orthogonal polynomials with respect to the weight functions
$x_1^{\alpha_1}\cdots x_d^{\alpha_d}$ on the unit sphere $S^{d1}$ in
$\RR^d$. The results include explicit formulae for orthonormal polynomials,
reproducing and Poisson kernel, as well as intertwining operator.
Keywords:Orthogonal polynomials in several variables, sphere, hharmonics Categories:33C50, 33C45, 42C10 
