39B05 General
39B12 Iteration theory, iterative and composite equations [See also 26A18, 30D05, 37-XX]
39B22 Equations for real functions [See also 26A51, 26B25]
39B32 Equations for complex functions [See also 30D05]
39B42 Matrix and operator equations [See also 47Jxx]
39B52 Equations for functions with more general domains and/or ranges
39B55 Orthogonal additivity and other conditional equations
39B62 Functional inequalities, including subadditivity, convexity, etc. [See also 26A51, 26B25, 26Dxx] 
39B72 Systems of functional equations and inequalities
39B82 Stability, separation, extension, and related topics [See also 46A22]
39B99 None of the above, but in this section