On the differentiability of functions
Volume 23 / 1964
                    
                    
                        Studia Mathematica 23 (1964), 247-283                    
                                        
                        DOI: 10.4064/sm-23-3-247-283                    
                                    
                                                                
                             
             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                         
                                                            