Allen, Bruce Observational Relativity and Cosmology, AEI-Hannover, MPI for Gravitational Physics, Max Planck Society;
CoMP86-103-669.pdf (Publisher version), 2MB
Allen, B., & Jacobson, T. (1986). Vector two-point functions in maximally symmetric spaces. Communications in Mathematical Physics, 103(4), 669-692. doi:10.1007/BF01211169.