@article{MAN_1973__203_162432,
     author = {James E. Williamson},
     title = {A {Ramsey-Type} {Problem} for {Paths} in {Digraphs.}},
     journal = {Mathematische Annalen},
     pages = {117--118},
     publisher = {mathdoc},
     volume = {203},
     year = {1973},
     zbl = {0239.05119},
     url = {http://geodesic.mathdoc.fr/item/MAN_1973__203_162432/}
}