Grant Schoenebeck Luca Trevisan Madhur Tulsiani A Linear Round Lower Bound for Lovasz-Schrijver SDP Relaxations of Vertex Cover. 205-216 2007 conf/coco/2007 IEEE Conference on Computational Complexity http://doi.ieeecomputersociety.org/10.1109/CCC.2007.2 db/conf/coco/coco2007.html#SchoenebeckTT07