41-XX Approximations and expansions {For approximation theory in the complex domain, see 30E05, 30E10; for trigonometric approximation and interpolation, see 42A10, 42A15; for numerical approximation, see 65Dxx} 61999
41-00 General reference works (handbooks, dictionaries, bibliographies, etc.) pertaining to approximations and expansions 57
41-01 Introductory exposition (textbooks, tutorial papers, etc.) pertaining to approximations and expansions 248
41-02 Research exposition (monographs, survey articles) pertaining to approximations and expansions 454
41-03 History of approximations and expansions [Consider also classification numbers from Section 01-XX] 167
41Axx Approximations and expansions {For approximation theory in the complex domain, see 30E05, 30E10; for trigonometric approximation and interpolation, see 42A10, 42A15; for numerical approximation, see 65Dxx} 60962
41A60 Asymptotic approximations, asymptotic expansions (steepest descent, etc.) [See also 30E15] 4006
41A63 Multidimensional problems [Should also be assigned at least one other classification number from Section 41-XX] 5055
41A65 Abstract approximation theory (approximation in normed linear spaces and other abstract spaces) 6479