@article{SF_1974__7_134011,
     author = {J.G. Horne},
     title = {SL(2) has no {C1-extension} to a half-space.},
     journal = {Semigroup forum},
     pages = {286--291},
     publisher = {mathdoc},
     volume = {7},
     year = {1974},
     zbl = {0276.22013},
     url = {http://geodesic.mathdoc.fr/item/SF_1974__7_134011/}
}