Hidders, Jan and Marrara, S. and Paredaens, J. and Vercammen, R. (2005) On the expressive power of xquery fragments. In: Bierman, G.M. and Koch, C. (eds.) Database Programming Languages: 10th International Symposium. Lecture Notes in Computer Science 3774. Springer, pp. 154-168. ISBN 9783540309512.