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:It is particularly used for the treatment of ovarian, testicular, esophageal, head and neck cancers (Liu et al., 1998; Mansour et al., 2002; Zicca et al., 2002; Hanigan and Devarajan, 2003).
Category: