Addressing a variety of theoretical cosmological problems, and emphasizing a mathematical approach, this volume nicely complements Peebles' Physical Cosmology (Princeton Series in Physics, 1971). Ryan and Shepley have concentrated on the structure of models of the universe. By using a modern termilogy that emphasizes the operator nature of vectors and tensors, as opposed to their components in a particular coordinate system, the authors develop modern tensor analysis to the point where it can be applied to general relativistic cosmology. They then use it to describe homogeneous cosmologies in considerable detail. Both students and researchers are likely to find these techniques especially useful. Among their subjects are: spaces with groups of motions; singularities; Taub-NUT-Misner space; Bianchitype models; Hamiltonian cosmology; and perturbations in anisotropic models. A brief section on observations is also included, as is a complete bibliography. A final section presents graded exercises that underscore the potential yet unrealized in this area of study. Originally published in 1975. The Princeton Legacy Library uses the latest print-on-demand techlogy to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.