1. H. Milton Stewart School of Industrial and Systems Engineering, Georgia Institute of Technology , Atlanta, GA 30332 , USA
2. Heinz College of Information Systems and Public Policy, Carnegie Mellon University , Pittsburgh, PA 15213 , USA
3. Department of Mathematics, Universitat Jaume I , Castelló de la Plana, Valencia 12071 , Spain
4. Escuela de Estadística, Universidad Nacional de Colombia , Medellín , Colombia