Comments on: Victor Reiner, The distribution of descents and length in a Coxeter group

Raphael Rouquier pointed out the following relevant reference: I. G. Macdonald, "The Poincare series of a Coxeter Group", Math. Ann. 199 (1972), 161-174. In particular, formulas (12) and (14) of the present paper are stated on page 173 of this reference.