Embedding of graphs in the projective plane
Volume 57 / 1965
                    
                    
                        Fundamenta Mathematicae 57 (1965), 195-203                    
                                        
                        DOI: 10.4064/fm-57-2-195-203                    
                                    
                                                                
                             
             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                         
                                                            