Abstract Harmonic Analysis 70 Functional Analysis 70 Functional analysis Harmonic analysis Operator Theory 21 Operator theory 21 Fourier Analysis 20 Fourier analysis 20 Mathematical analysis 14 Functions of complex variables 13 Lie groups 12 Topological Groups and Lie Groups 12 Topological groups 12 Probabilities 11 Probability Theory 11 Differential Equations 10 Differential equations 10 Analysis 9 Approximation theory 8 Approximations and Expansions 8 Functions of a Complex Variable 8 Global Analysis and Analysis on Manifolds 7 Global analysis (Mathematics) 7 Manifolds (Mathematics) 7 Several Complex Variables and Analytic Spaces 6 Signal processing 6 Signal, Speech and Image Processing 6 Dynamical Systems 5 Dynamical systems 5 Integral Transforms and Operational Calculus 5