Michael Alekhnovich Eli Ben-Sasson Linear Upper Bounds for Random Walk on Small Density Random 3-CNF. 352-361 2003 conf/focs/2003 FOCS http://doi.ieeecomputersociety.org/10.1109/SFCS.2003.1238209 db/conf/focs/focs2003.html#AlekhnovichB03