An inequality relating total mass and the area of a trapped surface in general relativity

Let M be a space-time which is asymptotically flat at past null infinity I-, satisfies the dominant energy condition and contains a trapped surface T. The authors show that if T can be connected to I- by means of a nonsingular null-hypersurface N, then m2>or=A/16 pi where m is the Bondi mass with respect to N and A in the area of T.