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:One approach, such as the three-step search (TSS)[1], and twodimensional logarithm search (TDL)[2], new three-step search (N3SS)[3], efficient three-step search (E3SS)[4], and cross search (CS)[5] employ coarse-to-fine searching to reduce the number of search points.
Category: