János Pach, Rom Pinchasi, Micha Sharir. Solution of Scott s problem on the number of directions determined by a point set in 3-space. In Jack Snoeyink, Jean-Daniel Boissonnat, editors, Proceedings of the 20th ACM Symposium on Computational Geometry, Brooklyn, New York, USA, June 8-11, 2004. pages 76-85, ACM, 2004. [doi]
Abstract is missing.