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:MD simulations were carried out on the clusters of personal computers (CROW) at the National Institute of Chemistry in Ljubljana [34], using the CHARMM biomolecular simulation program [35] and CHARMMing web server [36].
Category: