@article{CMUC_1991_32_2_a3,
     author = {Fitzpatrick, Simon and Calvert, Bruce},
     title = {Sets invariant under projections onto one  dimensional subspaces},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {227--232},
     year = {1991},
     volume = {32},
     number = {2},
     mrnumber = {1137783},
     zbl = {0756.52002},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1991_32_2_a3/}
}