@article{MOMA_1969__73_177475,
     author = {Martin Aigner},
     title = {Graphs and {Partial} {Orderings.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {385--396},
     year = {1969},
     volume = {73},
     zbl = {0184.27502},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1969__73_177475/}
}