The quadratic assignment problem suffers from the non-convex, non-concave form of its objective function. In this paper, five alternative representations of the problem are given, whose convexity-concavity properties can, in principle, be exploited to some advantage. © 1995.
White, D. J. (1995). Some concave-convex representations of the quadratic assignment problem. European Journal of Operational Research, 80(2), 418–424. https://doi.org/10.1016/0377-2217(93)E0215-J