Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques 15th International Workshop, APPROX 2012, and 16th International Workshop, RANDOM 2012, Cambridge, MA, USA, August 15-17, 2012. Proceedings - Gupta, Anupam; Jansen, Klaus; Rolim, José; Servedio, Rocco (Springer Berlin Heidelberg : Imprint: Springer, 2012)