The classification of pairs of binary quadratic forms
Volume 59 / 1991
                    
                    
                        Acta Arithmetica 59 (1991), 105-121                    
                                        
                        DOI: 10.4064/aa-59-2-105-121                    
                                    
                                                                
                             
             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                         
                                                            