[1] CORE,
[2] 34 Voie du Roman Pays,undefined
[3] 1348 Louvain-la-Neuve,undefined
[4] Belgium,undefined
[5] e-mail: defarias@core.ucl.ac.be,undefined
[6] School of Industrial and Systems Engineering,undefined
[7] Georgia Institute of Technology,undefined
[8] Atlanta,undefined
[9] GA 30332-0205,undefined
[10] USA,undefined
[11] e-mail: george.nemhauser@isye.gatech.edu Partially supported by NSF grants DMI-0100020 and DMI-0121495.,undefined