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:Several biologically-inspired algorithms have been applied to the HPlattice optimization problem, including memetic algorithms [5,6], particle swarm optimization [7], a contact interactions method [8], an immune algorithm [9] and ant colony optimization [10].
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