18-XX Category theory, homological algebra

• 18-00 General reference works (handbooks, dictionaries, bibliographies, etc.)
• 18-01 Instructional exposition (textbooks, tutorial papers, etc.)
• 18-02 Research exposition (monographs, survey articles)
• 18-03 Historical (must be assigned at least one classification number from 01-XX)
• 18-04 Explicit machine computation and programs (not the theory of computation or programming)
• 18-06 Proceedings, conferences, collections, etc.
• 18Axx General theory of categories and functors
• 18Bxx Special categories
• 18Cxx Categories and algebraic theories
• 18Dxx Categories with structure
• 18Exx Abelian categories
• 18Fxx Categories and geometry
• 18Gxx Homological algebra, see also {13Dxx, 16Exx, 55Uxx}