Global optimization solutions to a class of non-convex quadratic minimization problems with quadratic constraints

Expression of concern notes 'concerns regarding the peer review process'; Dates are unclear - expression of concern available before issue in which it is listed (Mar 2016, vol. 21, iss. 3); This article was later retracted - see also RW post: http://retractionwatch.com/2015/11/24/after-coordinating-peer-review-author-withdraws-special-issue-of-math-journal/ and http://retractionwatch.com/2016/01/12/math-journal-retracts-entire-issue-following-peer-review-problems/;