“…, n, are determined such that g(x) is convex. A generalization of this method using non-diagonal shifting appeared in Akrotirianakis et al [5] and Skjäl et al [38,39], and a different form of an understimator using exponentials instead of a quadratic function as a perturbation function was discussed in [3,4,14,15]. Other forms of convex and linear relaxations were investigated in Anstreicher [7], Domes and Neumaier [10], and Scott et al [37], for instance.…”