Warren P. Adams Monique Guignard Peter M. Hahn William L. Hightower A level-2 reformulation-linearization technique bound for the quadratic assignment problem. 983-996 2007 180 European Journal of Operational Research 3 http://dx.doi.org/10.1016/j.ejor.2006.03.051 db/journals/eor/eor180.html#AdamsGHH07