20C15 Ordinary representations and characters

20C20 Modular representations and characters

20C25 Projective representations and multipliers

20C30 Representations of finite symmetric groups

20C32 Representations of infinite symmetric groups

20C33 Representations of finite groups of Lie type

20C34 Representations of sporadic groups

20C35 Applications of group representations to physics

20C99 None of the above, but in this section

20D05 Finite simple groups and their classification

20D06 Simple groups: alternating groups and groups of Lie type [See also <a href="#code:20Gxx">20Gxx</a>]

20D10 Solvable groups, theory of formations, Schunck classes, Fitting classes, $\pi$-length, ranks [See also <a href="#code:20F17">20F17</a>]

20D20 Sylow subgroups, Sylow properties, $\pi$-groups, $\pi$-structure

20D25 Special subgroups (Frattini, Fitting, etc.)

20D60 Arithmetic and combinatorial problems

20D99 None of the above, but in this section

20Exx Structure and classification of infinite or finite groups

20E06 Free products, free products with amalgamation, Higman-Neumann-Neumann extensions, and generalizations

20E07 Subgroup theorems; subgroup growth

20E08 Groups acting on trees [See also <a href="#code:20F65">20F65</a>]

20E10 Quasivarieties and varieties of groups

20E15 Chains and lattices of subgroups, subnormal subgroups [See also <a href="#code:20F22">20F22</a>]

20E22 Extensions, wreath products, and other compositions [See also <a href="#code:20J05">20J05</a>]

20E26 Residual properties and generalizations; residually finite groups

20E32 Simple groups [See also <a href="#code:20D05">20D05</a>]

20E36 Automorphisms of infinite groups [For automorphisms of finite groups, see <a href="#code:20D45">20D45</a>]

20E42 Groups with a $BN$-pair; buildings [See also <a href="#code:51E24">51E24</a>]

20E99 None of the above, but in this section

20Fxx Special aspects of infinite or finite groups

20F05 Generators, relations, and presentations

20F06 Cancellation theory; application of van Kampen diagrams [See also <a href="#code:57M05">57M05</a>]