@article{IM_1969__7_141959,
     author = {R.G. SWAN},
     title = {Invariant {Rational} {Functions} and a {Problem} of {Steenrod.}},
     journal = {Inventiones mathematicae},
     pages = {148--158},
     publisher = {mathdoc},
     volume = {7},
     year = {1969},
     zbl = {0186.07601},
     url = {http://geodesic.mathdoc.fr/item/IM_1969__7_141959/}
}