E. Moet, M. van Kreveld, and A. van der Stappen. SCG '06: Proceedings of the Twenty-Second Annual Symposium on Computational geometry, page 177―186. New York, NY, USA, ACM, (2006)
M. van Kreveld, {. Schramm, and A. Wolff. Proc. 12th Internat. ACM Symp. Advances in Geographic Information Systems (ACM-GIS'04), page 222--231. ACM Press, New York, (2004)