(There is no original abstract.) These are lecture notes from a 1971 summer school surveying the then known cosmological models in particular the properties of Bianchi cosmologies, and giving a pedagogical introduction to groups of isometries in spacetime and to the orthonormal tetrad method.
Comments: These notes have been widely cited, but were not readily available. The copyright is held by Taylor and Francis who now own Gordon and Breach and whose permission must be sought for any uses demanding copyright. They have given permission for posting to archives, for which I am grateful, saying "Given that the material was pre-digital you are permitted to scan and post the printed original."
Journal: Carg\`ese Lectures in Physics, vol.6, ed. E. Schatzman, pages 61-174. Gordon and Breach, New York (1973)
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