04-XX Set theory [See also 03Exx]

• 04-00 General reference works (handbooks, dictionaries, bibliographies, etc.)
• 04-01 Instructional exposition (textbooks, tutorial papers, etc.)
• 04-02 Research exposition (monographs, survey articles)
• 04-03 Historical (must be assigned at least one classification number from Section 01)
• 04-04 Explicit machine computation and programs (not the theory of computation or programming)
• 04-06 Proceedings, conferences, collections, etc.
• 04A03 Set algebra
• 04A05 Relations, functions [See also 08A02]
• 04A10 Ordinal and cardinal numbers; generalizations \SeeAlso {03E10}
• 04A15 Descriptive set theory; Borel classifications, Suslin schemes, etc. [See also 03E15, 26A21, 28A05, 54H05]
• 04A20 Combinatorial set theory [See also 03E05, 05A05]; filters
• 04A25 Axiom of choice and equivalent propositions (Zorn's lemma, etc.) [See also 03E25]
• 04A30 Continuum hypothesis, generalized continuum hypothesis [See also 03E50, 54A25]
• 04A72 Fuzzy sets, fuzzy relations [See also 03E72, 94D05] {For fuzzy versions, see specific sections}
• 04A99 Miscellaneous topics