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 [42Xxx]  --  Fourier analysis 
  - [42Axx]  --  Fourier analysis in one variable 
    
      
        
            
            [42A05] 
            --  | 
          Trigonometric polynomials, inequalities, extremal problems | 
         
        
            
            [42A16] 
            --  | 
           Fourier coefficients, Fourier series of functions with special properties, special Fourier series | 
         
        
            
            [42A20] 
        --  | 
           Convergence and absolute convergence of Fourier and trigonometric series | 
         
        
            
            [42A32] 
        -- | 
          Trigonometric series of special types (positive coefficients, monotonic coefficients, etc.) | 
         
       
     
   
  - [42Bxx] 
    --  Fourier analysis in several variables
    
      
        
             [42B10]
    --   | 
          Fourier and Fourier-Stieltjes transforms and other transforms of Fourier type | 
         
        
             [42B20]
    -- | 
          Singular integrals (Calderón-Zygmund, etc.) | 
         
        
             [42B25]
            -- | 
           Maximal functions, Littlewood-Paley
            theory 
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