C. Cancelier et B. Franchi, SUBELLIPTIC-ESTIMATES FOR A CLASS OF DEGENERATE ELLIPTIC INTEGRODIFFERENTIAL OPERATORS, Mathematische Nachrichten, 183, 1997, pp. 19-41
In this paper we prove subelliptic estimates for operators of the form
Delta(z)+lambda(2)(x)S in IR(N)=IR(x)(n)xIR(y)(m), where the operator
S is an elliptic integro-differential operator in IR(N) and lambda is
a nonnegative Lipschitz continuous function.