A Jacobian condition for injectivity of differentiable plane maps
Tom 51 / 1990
                    
                    
                        Annales Polonici Mathematici 51 (1990), 249-254                    
                                        
                        DOI: 10.4064/ap-51-1-249-254                    
                                    
                                                                
                             
             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                         
                                                            