Kelly, Paul Joseph. The non-Euclidean hyperbolic plane : its structure and consistency / P. Kelly, G. Matthews. - New York : Springer-Verlag, 1981. - xiii, 333 p. ill. ; 24 cm. - Universitext . Includes index ISBN: 3540905529 (New York) 0387905529 (Berlin) Subjects--Topical Terms: Geometry, Hyperbolic