@article{10_21136_CMJ_1983_101878,
     author = {Zaj{\'\i}\v{c}ek, Lud\v{e}k},
     title = {Differentiability of the distance function and points of multi-valuedness of the metric projection in {Banach} space},
     journal = {Czechoslovak Mathematical Journal},
     pages = {292--308},
     year = {1983},
     volume = {33},
     number = {2},
     doi = {10.21136/CMJ.1983.101878},
     mrnumber = {699027},
     zbl = {0527.41028},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1983.101878/}
}