Arist Kojevnikov Dmitry Itsykson Lower Bounds of Static Lovász-Schrijver Calculus Proofs for Tseitin Tautologies. 323-334 2006 conf/icalp/2006-1 ICALP (1) http://dx.doi.org/10.1007/11786986_29 db/conf/icalp/icalp2006-1.html#KojevnikovI06