An example in Fourier series
Volume 10 / 1948
                    
                    
                        Studia Mathematica 10 (1948), 113-119                    
                                        
                        DOI: 10.4064/sm-10-1-113-119                    
                                    
                                                                
                             
             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                         
                                                            