Ehlers, Jürgen Geometric Analysis and Gravitation, AEI-Golm, MPI for Gravitational Physics, Max Planck Society;
336754.pdf (Publisher version), 2MB
Ehlers, J., & Rienstra, W. (1969). The-Locally Isotropic Solutions of the Liouville and Poisson Equations. Astrophysical Journal, 155: 1969ApJ..155.105E, pp. 105-116.