Konstantinos Georgiou Avner Magen Toniann Pitassi Iannis Tourlakis Tight integrality gaps for Vertex Cover SDPs in the Lovasz-Schrijver hierarchy. 2006 13 Electronic Colloquium on Computational Complexity (ECCC) http://eccc.hpi-web.de/eccc-reports/2006/TR06-152/index.html 152 db/journals/eccc/eccc13.html#GeorgiouMPT06