On power series in the differentiation operator
Volume 45 / 1973
                    
                    
                        Studia Mathematica 45 (1973), 309-317                    
                                        
                        DOI: 10.4064/sm-45-3-309-317                    
                                    
                                                                
                             
             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                         
                                                            