In these notes we investigate the ring of real polynomials in four variables, which are invariant under the action of the reflection groups [3, 4, 3] and [3, 3, 5]. It is well known that they are rationally generated in degree 2,6,8,12 and 2,12,20,30. We give a different proof of this fact by giving explicit equations for the generating polynomials. 0 Introduction There are four groups generate...