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Lee, John M. (1997). Riemannian Manifolds: An Introduction to Curvature. Graduate Texts in Mathematics. Vol. 176. New York: Springer-Verlag. ISBN 978-0-387-98322-6. OCLC 54850593.
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Lee, John M. (1997). Riemannian Manifolds: An Introduction to Curvature. Graduate Texts in Mathematics. Vol. 176. New York: Springer-Verlag. ISBN 978-0-387-98322-6. OCLC 54850593.