  In this note, a new proof for the positivity of Dunkl's intertwining operator
in the crystallographic case is given. It is based on an asymptotic
relationship between the Opdam-Cherednik kernel and the Dunkl kernel as
recently observed by M. de Jeu, and on positivity results of S. Sahi for the
Heckman-Opdam polynomials and their non-symmetric counterparts.
