Acknowledgment of priority
Tom 167 / 2015
                    
                    
                        Acta Arithmetica 167 (2015), 299-299                    
                                        
                        DOI: 10.4064/aa167-3-7                    
                                    
                                                                
                             
             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                         
                                                            