Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques : 10th International Workshop, APPROX 2007, and 11th International Workshop, RANDOM 2007, Princeton, NJ, USA, August 20-22, 2007, Proceedings - Moses Charikar, Klaus Jansen, Omer Reingold, José D. P. Rolim ((Lecture Notes in Computer Science))