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:• Even more efficient pure TSP heuristics such as the Lin-Kernighan heuristic (LKH) (Lin and Kernighan, 1973), using the LKH implementation (Helsgaun, 2000, http://www.
Category: