1. Abiteboul, S., Kanellakis, P., Grahne, G.: On the representation and querying of sets of possible worlds. Theoret. Comput. Sci. 78(1), 158–187 (1991)
2. Abiteboul, S., Hull, R., Vianu, V.: Foundations of Databases. Addison-Wesley, Reading (1995)
3. Abiteboul, S., Segoufin, L., Vianu, V.: Representing and querying XML with incomplete information. ACM TODS 31(1), 208–254 (2006)
4. Arenas, M., Barceló, P., Libkin, L., Murlak, F.: Foundations of Data Exchange. Cambridge University Press, Cambridge (2014)
5. Barceló, P., Libkin, L., Poggi, A., Sirangelo, C.: XML with incomplete information. J. ACM 58(1), 238–272 (2010)