@Article{DinurSafra05,
  author =       "Dinur, Irit and Safra, Shmuel",
  title =        "On the hardness of approximating minimum vertex cover",
  journal =    "Annals of Mathematics",
  volume =      "162",
  number =      "1",
  pages = 	"439--485",
  year =        "2005",
}