@article{MOMA_1980__89_177951,
     author = {Frank Piefke},
     title = {Ma{\ss}e f\"ur gerichtete {Geraden} und nicht-symmetrische {Pseudometriken} in der {Ebene} {II.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {45--56},
     publisher = {mathdoc},
     volume = {89},
     year = {1980},
     zbl = {0423.60014},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1980__89_177951/}
}