Boris Bukh, Jirà Matousek, Gabriel Nivasch. Lower bounds for weak epsilon-nets and stair-convexity. In John Hershberger, Efi Fogel, editors, Proceedings of the 25th ACM Symposium on Computational Geometry, Aarhus, Denmark, June 8-10, 2009. pages 1-10, ACM, 2009. [doi]
Abstract is missing.