Roberto Bagnara Patricia M. Hill Enea Zaffanella An Improved Tight Closure Algorithm for Integer Octagonal Constraints. 8-21 2008 VMCAI http://dx.doi.org/10.1007/978-3-540-78163-9_6 conf/vmcai/2008 db/conf/vmcai/vmcai2008.html#BagnaraHZ08