Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:The Simulated Annealing approach has been proven to be very effective when applied to non convex optimization, for which gradient based algorithms may fail to produce good solutions, Cerný (1985); Marques et al. (1991); A.
Category: