Friedrich, Helmut Geometric Analysis and Gravitation, AEI-Golm, MPI for Gravitational Physics, Max Planck Society;
Journal-of-Geometry-and-Physics_24_2.pdf (Publisher version), 5MB
Friedrich, H. (1998). Gravitational fields near space-like and null infinity. Journal of Geometry and Physics, 24(2), 83-163. doi:10.1016/S0393-0440(97)82168-7.