Ahmet B. Keha Ismael R. de Farias Jr. George L. Nemhauser Models for representing piecewise linear cost functions. 44-48 2004 32 Oper. Res. Lett. 1 http://dx.doi.org/10.1016/S0167-6377(03)00059-2 db/journals/orl/orl32.html#KehaFN04