54H13 Topological fields, rings, etc. [See also <a href="#code:12Jxx">12Jxx</a>] {For algebraic aspects, see <a href="#code:13Jxx">13Jxx</a>, <a href="#code:16W80">16W80</a>}

54H15 Transformation groups and semigroups [See also <a href="#code:20M20">20M20</a>, <a href="#code:22-XX">22-XX</a>, <a href="#code:57Sxx">57Sxx</a>]

54H20 Topological dynamics [See also <a href="#code:28Dxx">28Dxx</a>, <a href="#code:37Bxx">37Bxx</a>]

54H25 Fixed-point and coincidence theorems [See also <a href="#code:47H10">47H10</a>, <a href="#code:55M20">55M20</a>]

54H99 None of the above, but in this section

54Jxx Nonstandard topology [See also <a href="#code:03H05">03H05</a>]

54J05 Nonstandard topology [See also <a href="#code:03H05">03H05</a>]

54J99 None of the above, but in this section

55-00 General reference works (handbooks, dictionaries, bibliographies, etc.)

55-01 Instructional exposition (textbooks, tutorial papers, etc.)

55-02 Research exposition (monographs, survey articles)

55-03 Historical (must also be assigned at least one classification number from Section 01)

55-04 Explicit machine computation and programs (not the theory of computation or programming)

55-06 Proceedings, conferences, collections, etc.

55Mxx Classical topics {For the topology of Euclidean spaces and manifolds, see <a href="#code:57Nxx">57Nxx</a>}

55M10 Dimension theory [See also <a href="#code:54F45">54F45</a>]

55M15 Absolute neighborhood retracts [See also <a href="#code:54C55">54C55</a>]

55M20 Fixed points and coincidences [See also <a href="#code:54H25">54H25</a>]

55M30 Ljusternik-Schnirelman (Lyusternik-Shnirel&apos;man) category of a space

55M35 Finite groups of transformations (including Smith theory) [See also <a href="#code:57S17">57S17</a>]

55M99 None of the above, but in this section

55Nxx Homology and cohomology theories [See also <a href="#code:57Txx">57Txx</a>]

55N15 $K$-theory [See also <a href="#code:19Lxx">19Lxx</a>] {For algebraic $K$-theory, see <a href="#code:18F25">18F25</a>, <a href="#code:19-XX">19-XX</a>}