20XX 


Group theory and generalizations 

20Exx 

Structure and classification of infinite or finite groups 


20E05 
Free nonabelian groups 


20E06 
Free products, free products with amalgamation, HigmanNeumannNeumann extensions, and generalizations 


20E07 
Subgroup theorems; subgroup growth 


20E08 
Groups acting on trees [See also 20F65] 


20E10 
Quasivarieties and varieties of groups 


20E15 
Chains and lattices of subgroups, subnormal subgroups [See also 20F22] 


20E18 
Limits, profinite groups 


20E22 
Extensions, wreath products, and other compositions [See also 20J05] 


20E25 
Local properties 


20E26 
Residual properties and generalizations 


20E28 
Maximal subgroups 


20E32 
Simple groups [See also 20D05] 


20E34 
General structure theorems 


20E36 
General theorems concerning automorphisms of groups 


20E42 
Groups with a $BN$pair; buildings [See also 51E24] 


20E45 
Conjugacy classes 


20E99 
None of the above, but in this section 