@article{DCG_1991__6_4_131161,
     author = {K. Mulmuley},
     title = {On {Levels} in {Arrangements} and {Voronoi} {Diagrams.}},
     journal = {Discrete & computational geometry},
     pages = {307--338},
     publisher = {mathdoc},
     volume = {6},
     number = {4},
     year = {1991},
     zbl = {0727.68129},
     url = {http://geodesic.mathdoc.fr/item/DCG_1991__6_4_131161/}
}