Andrés Weintraub Pohorille Professor Department of Industrial Engineering University of Chile República 701, Santiago, Chile Mailing Address: Professor Andrés Weintraub P.O. Box 2777 Santiago, Chile Tel: (56 2) 678-4046 Fax: (56 2) 689-7895 e-mail: aweintra@dii.uchile.cl http://www.dii.uchile.cl/~aweintra