5100  General reference works (handbooks, dictionaries, bibliographies, etc.) 
5101  Instructional exposition (textbooks, tutorial papers, etc.) 
5102  Research exposition (monographs, survey articles) 
5103  Historical (must also be assigned at least one classification number from Section 01) 
5104  Explicit machine computation and programs (not the theory of computation or programming) 
5106  Proceedings, conferences, collections, etc. 


51Axx  Linear incidence geometry 
51Bxx  Nonlinear incidence geometry 
51C05  Ring geometry (Hjelmslev, Barbilian, etc.) 
51Dxx  Geometric closure systems 
51Exx  Finite geometry and special incidence structures 
51Fxx  Metric geometry 
51G05  Ordered geometries (ordered incidence structures, etc.) 
51Hxx  Topological geometry 
51Jxx  Incidence groups 
51Kxx  Distance geometry 
51Lxx  Geometric order structures [See also 53C75] 
51Mxx  Real and complex geometry 
51Nxx  Analytic and descriptive geometry 
51P05  Geometry and physics (should also be assigned at least one other classification number from Sections 7086) 