40-00 General reference works (handbooks, dictionaries, bibliographies, etc.)
40-01 Instructional exposition (textbooks, tutorial papers, etc.)
40-02 Research exposition (monographs, survey articles)
40-03 Historical (must also be assigned at least one classification number from Section 01)
40-04 Explicit machine computation and programs (not the theory of computation or programming)
40-06 Proceedings, conferences, collections, etc.
40Axx Convergence and divergence of infinite limiting processes
40B05 Multiple sequences and series {(should also be assigned at least one other classification number in this section)}
40Cxx General summability methods
40Dxx Direct theorems on summability
40Exx Inversion theorems
40F05 Absolute and strong summability
40Gxx Special methods of summability
40H05 Functional analytic methods in summability
40J05 Summability in abstract structures [See also 43A55, 46A35, 46B15]