@article{JRAM_1960__203_150427,
     author = {G\"unter Ewald and LeRoy M. Kelly},
     title = {Tangents in {Real} {Banach} {Spaces.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {160--173},
     publisher = {mathdoc},
     volume = {203},
     year = {1960},
     zbl = {0094.35105},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1960__203_150427/}
}