Functional analysis Functional Analysis 980 Differential Equations 284 Differential equations 284 Operator theory 277 Operator Theory 276 Mathematical analysis 165 Mathematical physics 147 Analysis 140 Probabilities 116 Probability Theory 114 Mathematical optimization 106 Mathematics 105 Functions of complex variables 95 Measure theory 86 Measure and Integration 84 Calculus of variations 79 Functions of a Complex Variable 79 Applications of Mathematics 78 Calculus of Variations and Optimization 78 Abstract Harmonic Analysis 70 Harmonic analysis 70 Fourier Analysis 69 Fourier analysis 69 Mathematical Methods in Physics 66 Functions of real variables 63 Real Functions 61 Topology 60 Approximation theory 59 Approximations and Expansions 59