3900  General reference works (handbooks, dictionaries, bibliographies, etc.)


3901  Instructional exposition (textbooks, tutorial papers, etc.)


3902  Research exposition (monographs, survey articles)


3903  Historical (must also be assigned at least one classification number from Section 01)


3904  Explicit machine computation and programs (not the theory of computation or programming)


3906  Proceedings, conferences, collections, etc.



39Axx  Difference equations {For dynamical systems, see 37XX}

39Bxx  Functional equations and inequalities [See also 30D05]
