Correction to: On the Solvability of a Class of Second Order Degenerate Operators

In this paper we will be concerned with the problem of solvability of second order degenerate operators that are not of principal type. We will describe some recent results we have obtained about local solvability in the Sobolev spaces of a class of degenerate operators which is an elaboration of the class considered by Colombini-Cordaro-Pernazza (in turn, an elaboration of the adjoint of the Kannai operator)