1. http://my.safaribooksonline.com/book/databases/xml/0201844524/contributors/art01lev1sec21.
2. Bruno, N., Koudas, N., Srivastava, D.: Holistic twig joins: optimal XML pattern matching. In: SIGMOD'02, ACM Press, New York, 2002.
3. Grinev, M., Pleshachkov, P.: Rewriting-based Optimization for XQuery Transformational Queries. In: IDEAS'05, IEEE Computer Society Press, Los Alamitos, 2005.
4. Jagadish, H.V., Lakshmanan, L.V.S., Scannapieco, M., Srivastava, D., Wiwatwattana, N.: Colorful XML: One Hierarchy Isn't Enough. In: SIGMOD'04, ACM Press, New York, 2004.
5. Lapis, G.: XML and Relational Storage-Are they mutually exclusive. IBM Corporation, 2005.