1. Gupta, A., Harinarayan, V., Rajaraman, A.: Virtual database technology. SIGMOD Record 26, 57–61 (1997)
2. Gottlob, G., Koch, C.: Monadic datalog and the expressive power of languages for web information extraction. In: Proc. of the 21th PODS, pp. 17–28 (2002)
3. Gottlob, G., Koch, C.: Monadic queries over tree-structured data. In: Proceedings of the 17th IEEE Symposium on Logic in Computer Science, pp. 189–202 (2002)
4. Li, Z., Ng, W.K.: Wiccap: From semi-structured data to structured data. In: Proc. of 11th IEEE International Conference on the ECBS (2004)
5. Baumgartner, R., Flesca, S., Gottlob, G.: Visual web information extraction with lixto. In: Proc. of 27th International Conference on Very Large Data Bases, Roma, Italy, pp. 119–128. Morgan Kaufmann, San Francisco (2001)