Karen Aardal Stan P. M. van Hoesel Arie M. C. A. Koster Carlo Mannino Antonio Sassano Models and solution techniques for frequency assignment problems. 261-317 2003 1 4OR 4 http://dx.doi.org/10.1007/s10288-003-0022-6 db/journals/4or/4or1.html#AardalHKMS03