@article{MS2_1967__20_165991,
     author = {G\"osta Wahde},
     title = {A {Closure} {Problem} for {Spaces} of {Infinitely} {Differentiable} {Functions.}},
     journal = {Mathematica Scandinavica},
     pages = {209--224},
     publisher = {mathdoc},
     volume = {20},
     year = {1967},
     zbl = {0197.38902},
     url = {http://geodesic.mathdoc.fr/item/MS2_1967__20_165991/}
}