An Optimal Algorithm for the (<= k)-Levels, with Applications to Separation and Transversal Problems.

Hazel Everett Jean-Marc Robert Marc J. van Kreveld An Optimal Algorithm for the (<= k)-Levels, with Applications to Separation and Transversal Problems. 38-46 1993 Symposium on Computational Geometry http://doi.acm.org/10.1145/160985.160994 db/conf/compgeom/compgeom93.html#EverettRK93