# Category Theory/References
### Textbooks freely available online

* Adámek, Jiří, Herrlich, Horst, & Strecker, George E. (1990) Abstract and concrete categories. John Wiley & Sons. ISBN 0-471-60922-6.
* Barr, Michael and Wells, Charles (2012) Category Theory for Computing Science.
* ——— (2002) Toposes, triples and theories. Revised and corrected version of the Springer-Verlag book (1983).
* Freyd, Peter J. (1964) Abelian Categories. New York: Harper and Row.
* Goldblatt, R (1984) Topoi: the Categorial Analysis of Logic A clear introduction to categories, with particular emphasis on the recent applications to logic.
* Hillman, Chris Categorical primer, Formal introduction to Category Theory.
* Leinster, Tom (2004) Higher operads, higher categories (London Math. Society Lecture Note Series 298). Cambridge Univ. Press.
* Martini, A.,Ehrig, H., and Nunes, D. (1996) Elements of Basic Category Theory (Technical Report 96-5, Technical University Berlin)
* Schalk, A. and Simmons, H. (2005) An introduction to Category Theory in four easy movements. Notes for a course offered as part of the MSc. in Mathematical Logic, Manchester University.
* Spivak, David I. (2013) Category Theory for Scientists.
* Turi, Daniele (1996–2001) Category Theory Lecture Notes. Based on Mac Lane (1998).

### Other textbooks

* Awodey, Steven (2006). Category Theory (Oxford Logic Guides 49). Oxford University Press.
* Borceux, Francis (1994). Handbook of categorical algebra (Encyclopedia of Mathematics and its Applications 50-52). Cambridge Univ. Press.
* Freyd, Peter J. & Scedrov, Andre, (1990). Categories, allegories (North Holland Mathematical Library 39). North Holland.
* Hatcher, William S. (1982). The Logical Foundations of Mathematics, 2nd ed. Pergamon. Chpt. 8 is an idiosyncratic introduction to category theory, presented as a first order theory.
* Lawvere, William, & Rosebrugh, Robert (2003). Sets for mathematics. Cambridge University Press.
* Lawvere, William, & Schanuel, Steve (1997). Conceptual mathematics: a first introduction to categories. Cambridge University Press.
* Leinster, Tom, Basic Category Theory, Cambridge University Press, 2014.
* McLarty, Colin (1991). Elementary Categories, Elementary Toposes. Oxford University Press.
* Mac Lane, Saunders (1998). Categories for the Working Mathematician'. 2nd ed. (Graduate Texts in Mathematics 5). Springer-Verlag.
* ——— and Garrett Birkhoff (1967). Algebra. 1999 reprint of the 2nd ed., Chelsea. ISBN 0-8218-1646-2. An introduction to the subject making judicious use of category theoretic concepts, especially commutative diagrams.
* May, Peter (1999). A Concise Course in Algebraic Topology. University of Chicago Press, ISBN 0-226-51183-9.
* Pedicchio, Maria Cristina & Tholen, Walter (2004). Categorical foundations (Encyclopedia of Mathematics and its Applications 97). Cambridge University Press.
* Pierce, Benjamin (1991). Basic Category Theory for Computer Scientists. MIT Press.
* Taylor, Paul (1999). Practical Foundations of Mathematics. Cambridge University Press. An introduction to the connection between category theory and constructive mathematics.

### External links

* Stanford Encyclopedia of Philosophy: "Category Theory" -- by Jean-Pierre Marquis. Extensive bibliography.
* Homepage of the Categories mailing list, with extensive resource list.
* Baez, John, 1996,"The Tale of n-categories." An informal introduction to higher order categories.
* The catsters" a Youtube channel about category theory.
* PlanetMath article on category theory
* Categories, Logic and the Foundations of Physics, Webpage dedicated to the use of Categories and Logic in the Foundations of Physics.
* Interactive Web page which generates examples of categorical constructions in the category of finite sets. Written by Jocelyn Paine
* n-Category Café a group blog with some emphasis on higher categories.
* n-Lab wiki-lab with many short articles on topics in category theory.