D. Arthur, und S. Vassilvitskii. SCG '06: Proceedings of the twenty-second annual symposium on Computational geometry, Seite 144--153. New York, NY, USA, ACM, (2006)
D. Harel, H. Kugler, und A. Pnueli. Formal Methods in Software and Systems Modeling: Essays Dedicated to Hartmut Ehrig on the Occasion of His 60th Birthday, Seite 309--324. Department of Computer Science and Applied Mathematics, The Weizmann Institute of Science, Rehovot, Israel, Springer, (2005)