- 12-00 General reference works (handbooks, dictionaries, bibliographies, etc.)
- 12-01 Instructional exposition (textbooks, tutorial papers, etc.)
- 12-02 Research exposition (monographs, survey articles)
- 12-03 Historical (must be assigned at least one classification number from 01-XX)
- 12-04 Explicit machine computation and programs (not the theory of computation or programming)
- 12-06 Proceedings, conferences, collections, etc.
- 12Dxx Real and complex fields
- 12Exx General field theory
- 12Fxx Field extensions
- 12Gxx Homological methods (field theory)
- 12Hxx Differential and difference algebra
- 12Jxx Topological fields
- 12Kxx Generalizations of fields
- 12Lxx Connections with logic
- 12Y05 Computational aspects of field theory and polynomials