@article{ELMA_1969__24_140926,
     author = {G. Chartrand and M. Behzad},
     title = {Line-Coloring of {Signed} {Graphs.}},
     journal = {Elemente der Mathematik},
     pages = {49--52},
     publisher = {mathdoc},
     volume = {24},
     year = {1969},
     zbl = {0175.50302},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1969__24_140926/}
}