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http://www.activemath.org/
2. Cabri home,
http://www.cabri.com/
3. Chen, X., Huang, Y., Wang, D.: On the design and implementation of a geometric knowledge base. In: Kauers, M., Wu, M., Zeng, Z. (eds.) ADG 2008, pp. 62–78. East China Normal University, China (2008)
4. Lecture Notes in Artificial Intelligence;X. Chen,2007
5. Chen, X., Wang, D.: Management of geometric knowledge in textbooks. Preprint, LMIB – Beihang University, China (November 2009)