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 beneficial role of PBM as supportive modality in the management of postmastectomy lymphedema is well established based on strong evidence [15, 16] and recent data suggest its beneficial role concerning radiation-induced oral mucositis [17–20].
Category: