18G10 Resolutions; derived functors [See also <a href="#code:13D02">13D02</a>, <a href="#code:16E05">16E05</a>, <a href="#code:18E25">18E25</a>]

18G15 Ext and Tor, generalizations, Künneth formula [See also <a href="#code:55U25">55U25</a>]

18G20 Homological dimension [See also <a href="#code:13D05">13D05</a>, <a href="#code:16E10">16E10</a>]

18G25 Relative homological algebra, projective classes

18G30 Simplicial sets, simplicial objects (in a category) [See also <a href="#code:55U10">55U10</a>]

18G35 Chain complexes [See also <a href="#code:18E30">18E30</a>, <a href="#code:55U15">55U15</a>]

18G40 Spectral sequences, hypercohomology [See also <a href="#code:55Txx">55Txx</a>]

18G99 None of the above, but in this section

19-00 General reference works (handbooks, dictionaries, bibliographies, etc.)

19-01 Instructional exposition (textbooks, tutorial papers, etc.)

19-02 Research exposition (monographs, survey articles)

19-03 Historical (must also be assigned at least one classification number from Section 01)

19-04 Explicit machine computation and programs (not the theory of computation or programming)

19-06 Proceedings, conferences, collections, etc.

19Axx Grothendieck groups and $K_0$ [See also <a href="#code:13D15">13D15</a>, <a href="#code:18F30">18F30</a>]

19A13 Stability for projective modules [See also <a href="#code:13C10">13C10</a>]

19A22 Frobenius induction, Burnside and representation rings

19A99 None of the above, but in this section

19B28 $K_1$ of group rings and orders [See also <a href="#code:57Q10">57Q10</a>]

19B37 Congruence subgroup problems [See also <a href="#code:20H05">20H05</a>]

19B99 None of the above, but in this section

19C09 Central extensions and Schur multipliers

19C20 Symbols, presentations and stability of $K_2$

19C99 None of the above, but in this section

19D23 Symmetric monoidal categories [See also <a href="#code:18D10">18D10</a>]

19D50 Computations of higher $K$-theory of rings [See also <a href="#code:13D15">13D15</a>, <a href="#code:16E20">16E20</a>]

19D55 $K$-theory and homology; cyclic homology and cohomology [See also <a href="#code:18G60">18G60</a>]