@article{MS2_1978__42_166590,
     author = {K\"ate Fenchel},
     title = {On a theorem of {Frobenius.}},
     journal = {Mathematica Scandinavica},
     pages = {243--250},
     publisher = {mathdoc},
     volume = {42},
     year = {1978},
     zbl = {0392.20015},
     url = {http://geodesic.mathdoc.fr/item/MS2_1978__42_166590/}
}