Key points are not available for this paper at this time.
For isolated gravitating systems of physical interest, the difference between the Arnowitt-Deser-Misner four-momentum and the Bondi four-momentum associated with a retarded instant of time is shown to equal the four-momentum carried away by the gravitational radiation emitted between infinite past and the given retarded instant.
Ashtekar et al. (Mon,) studied this question.