Fabio Grandi Federica Mandreoli Paolo Tiberio Marco Bergonzini A temporal data model and management system for normative texts in XML format. 29-36 2003 conf/widm/2003 WIDM http://doi.acm.org/10.1145/956699.956706 db/conf/widm/widm2003.html#GrandiMTB03