@article{MZ_1974__137_172052,
     author = {Roger D. Nussbaum},
     title = {On the {Uniqueness} of the {Topological} {Degree} for {k-Set-Contractions.}},
     journal = {Mathematische Zeitschrift},
     pages = {1--6},
     publisher = {mathdoc},
     volume = {137},
     year = {1974},
     zbl = {0268.55009},
     url = {http://geodesic.mathdoc.fr/item/MZ_1974__137_172052/}
}