Ehlers, Jürgen Geometric Analysis and Gravitation, AEI-Golm, MPI for Gravitational Physics, Max Planck Society;
Ehler_LNP28.pdf (Any fulltext), 2MB
Ehlers, J. (1974). Kinetic theory of gases in general relativity theory. In Lectures in Statistical Physics (pp. 78-105). Berlin, Heidelberg: Springer.