On ratio sets of natural numbers
Tom 15 / 1969
                    
                    
                        Acta Arithmetica 15 (1969), 273-278                    
                                        
                        DOI: 10.4064/aa-15-3-273-278                    
                                    
                                                                
                             
             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                         
                                                            