Your search returned the following 4 documents:

4. Approximating Covering Problems by Randomized Search Heuristics using Multi-Objective Models
   Tobias Friedrich, Jun He, Nils Hebbinghaus, Frank Neumann, and Carsten Witt
   Evolutionary Computation 18 (4): 617 - 633, 2010
   
3. Analyses of Simple Hybrid Algorithms for the Vertex Cover Problem
   Tobias Friedrich, Jun He, Nils Hebbinghaus, Frank Neumann, and Carsten Witt
   Evolutionary Computation, 17 (1): 3-19, 2009
   
2. Approximating Covering Problems by Randomized Search Heuristics Using Multi-Objective Models
   Tobias Friedrich, Jun He, Nils Hebbinghaus, Frank Neumann, and Carsten Witt
   In: Genetic and Evolutionary Computation Conference 2007, London, UK, 2007, 797-804
   
1. On Improving Approximate Solutions by Evolutionary Algorithms
   Tobias Friedrich, Jun He, Nils Hebbinghaus, Frank Neumann, and Carsten Witt
   In: IEEE Congress on Evolutionary Computation 2007, Singapore, Singapore, 2007, 2614-2621