Critical modulars
Volume 31 / 1968
                    
                    
                        Studia Mathematica 31 (1968), 451-453                    
                                        
                        DOI: 10.4064/sm-31-5-451-453                    
                                    
                                                                
                             
             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                         
                                                            