@article{MZ_1981__178_173121,
     author = {Robert Switzer},
     title = {Counting {Elemnts} in {Homotopy} {Sets.}},
     journal = {Mathematische Zeitschrift},
     pages = {527--554},
     publisher = {mathdoc},
     volume = {178},
     year = {1981},
     zbl = {0498.55006},
     url = {http://geodesic.mathdoc.fr/item/MZ_1981__178_173121/}
}