| MSC 1991 | Number of Preprints | |
| 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
| - | |
| 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
| 6 | browse |
| 18Bxx | Special categories
| 28 | browse |
| 18Cxx | Categories and algebraic theories
| 5 | browse |
| 18Dxx | Categories with structure
| 18 | browse |
| 18Exx | Abelian categories
| 5 | browse |
| 18Fxx | Categories and geometry
| 3 | browse |
| 18Gxx | Homological algebra
| 7 | browse |