M. van Kreveld, and J. Luo. Proceedings of the 15th annual ACM international symposium on Advances in geographic information systems, page 44:1--44:4. New York, NY, USA, ACM, (2007)
B. Kuijpers, B. Moelans, W. Othman, and A. Vaisman. Advances in Spatial and Temporal Databases, volume 5644 of Lecture Notes in Computer Science, Springer, Berlin / Heidelberg, (2009)