Background on Ricci flow
 "The Ricci flow: an introduction" by B. Chow and D. Knopf, Mathematical Surveys and Monographs 110, American Mathematical Society, Providence, RI, 2004.
 "The formation of singularities in the Ricci flow", by R. Hamilton, Surveys in differential geometry, Vol. II (Cambridge, MA, 1993), Internat. Press, Cambridge, MA, p. 7-136 (1995)
Background on the Geometrization Conjecture
 "Recent progress on the Poincare conjecture and the classification of 3-manifolds" by J. Morgan, Bull. Amer. Math. Soc. 42, p. 57-78 (2005)
Background on Differential Geometry :
 "Riemannian geometry" by P. Petersen, Graduate Texts in Mathematics 171, Springer-Verlag, New York, 1998.
 "A course in metric geometry" by D. Burago, Y. Burago and S. Ivanov, Graduate Studies in Mathematics 33, American Mathematical Society, Providence, RI, 2001.
 "Comparison theorems in Riemannian geometry" by J. Cheeger and D. Ebin, North-Holland Mathematical Library, Vol. 9. North-Holland Publishing Co., 1975.
Perelman's Work on Ricci Flow
 "The entropy formula for the Ricci flow and its geometric applications", by G. Perelman
 "Ricci flow with surgery on three-manifolds", by G. Perelman
 "Notes on Perelman's papers", by B. Kleiner and J. Lott
 "Minimal submanifolds", by T. Colding and W. Minicozzi
 Estimates for the extinction time for the Ricci flow on certain 3-manifolds and a question of Perelman, Tobias H. Colding; William P. Minicozzi II Journal: J. Amer. Math. Soc. 18 (2005), 561-569.
 Finite extinction time for the solutions to the Ricci flow on certain three-manifolds, Grisha Perelman, July 17, 2003, revised June 12, 2005