Acta Mathematica Sinica English Series · 2004 · 13 citations · 5 references
Natural SciencesMathematicsAlgebraHarmonic AnalysisHilbert Space FormalismOperator TheorySpecial FunctionsSpectral TheoryHermite FunctionsSubnormal OperatorsTheta Functions
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Hypoelliptic second order differential equations
Lars Hörmander · Acta Mathematica · 1967 · 2.4K citations · Full text
Gerald B. Folland, E. M. Stein · Communications on Pure and Applied Mathematics · 1974 · 972 citations