@article{MAN_1983__264_163788,
     author = {U. Abresch},
     title = {Isoparametric {Hypersurfaces} with {Four} or {Six} {Distinct} {Principal} {Curvatures.}  {Necessary} {Conditions} on the {Multiplicities.}},
     journal = {Mathematische Annalen},
     pages = {283--302},
     publisher = {mathdoc},
     volume = {264},
     year = {1983},
     zbl = {0505.53027},
     url = {http://geodesic.mathdoc.fr/item/MAN_1983__264_163788/}
}