Approximation, Randomization and Combinatorial Optimization. Algorithms and Techniques : 11th International Workshop, APPROX 2008 and 12th International Workshop, RANDOM 2008, Boston, MA, USA, August 25-27, 2008 - Ashish Goel, Klaus Jansen, José D. P. Rolim, Ronitt Rubinfeld ((Lecture Notes in Computer Science))