@article{MS2_1977__41_166553,
     author = {Ulrich Koschorke and Brian Sanderson},
     title = {Geometric interpretations of the generalized {Hopf} invariant.},
     journal = {Mathematica Scandinavica},
     pages = {199--217},
     year = {1977},
     volume = {41},
     zbl = {0385.55006},
     url = {http://geodesic.mathdoc.fr/item/MS2_1977__41_166553/}
}