Generation of Invariants,

Let G be any group acting on the Weyl algebra W1( ). We shall propose a method for finding explicit generators of the ring of invariants W1( )G. This method can be generalized to the case of the ring of invariants of an almost normalizing extension R over a commutative ring C under the linear action of a finite group G, provided that G is invertible in C and a set of explicit generators of gr(R)G is known.