Calì, Andrea and Martinenghi, D. and Carbotta, D. (2007) Query optimisation for web data sources: minimisation of the number of accesses. In: Ceci, M. and Malerba, D. and Tanca, L. (eds.) Proceedings of the Fifteenth Italian Symposium on Advanced Database Systems. Dipartimento di Informatica: Università degli Studi, pp. 316-323.