Sebastian Seibert Thomas Wilke Bounds for Approximating MAXLINEQ3-2 and MAXEKSAT. 179-212 1997 conf/dagstuhl/1997proof Lectures on Proof Verification and Approximation Algorithms http://dx.doi.org/10.1007/BFb0053017 db/conf/dagstuhl/proof1997.html#SeibertW97