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 author of case series of human patients stated that as the window width was increased, the foreign bodies were more easily identified and better differentiated from a gas or fluid build up due to the wood’s absorptive characteristics and the duration of the injury.(15)
Category: