$n$-dimensional polytopes 1 Approximation by arbitrary linear expressions 1 Approximations and expansions Basic linear algebra 1 Communication, information 1 Convex and discrete geometry 1 Convex sets in $n$ dimensions (including convex hypersurfaces) 1 more ... Frames (Vector analysis) 1 General convexity 1 General harmonic expansions, frames 1 Harmonic analysis in one variable 1 Harmonic analysis on Euclidean spaces 1 Hilbert space 1 Information and communication, circuits 1 Inverse problems 1 Linear and multilinear algebra; matrix theory 1 Mathematical programming 1 Nonconvex programming, global optimization 1 None of the above, but in this section 1 Nonlinear algebraic or transcendental equations 1 Nontrigonometric harmonic analysis 1 Numerical analysis 1 Operations research, mathematical programming 1 Operator theory 1 Polytopes and polyhedra 1 Signal theory (characterization, reconstruction, filtering, etc.) 1 Special classes of linear operators 1 Systems of equations 1 Trigonometric approximation 1 less ...