@article{DCG_1993__10_2_131282,
     author = {M. Sharir and B. Aronov and D.Q. Naiman and J. Pack},
     title = {An {Invariant} {Property} of {Balls} in {Arrangements} of {Hyperplanes.}},
     journal = {Discrete & computational geometry},
     pages = {421--426},
     publisher = {mathdoc},
     volume = {10},
     number = {2},
     year = {1993},
     zbl = {0788.52013},
     url = {http://geodesic.mathdoc.fr/item/DCG_1993__10_2_131282/}
}