http://publish.uwo.ca/~jbell/catlogprime.pdf (PDF)* Saunders Mac Lane and Ieke Moerdijk: "Sheaves in Geometry and Logic: a First Introduction to Topos Theory", Springer, New York, 1992.
* Saunders Mac Lane and Ieke Moerdijk (1992) "Sheaves in Geometry and Logic: a First Introduction to Topos Theory".