LetVbe a complex vector space of dimensionland letG⊂GL(V) be a finite reflection group. LetSbe theC-algebra of polynomial functions onVwith its usualG-module structure (gf)(v) =f{g-1v). LetRbe the subalgebra ofG-invariant polynomials. By Chevalley’s theorem there exists a setℬ= {f1, …,fl} of homogeneous polynomials such thatR=C[f1, …,fl]. We callℬa set of basic invariants or abasic setforG. The degreesdi= degfiare uniquely determined byG. We agree to number them so thatd1≤ … ≤di. The mapτ:V/G → C1defined by