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:…tool for clinicians interested in understanding the impact of drug therapy on the control of HIV and the associated problem of drug resistance (Bonhoeffer et al. 1997; Callaway and Perelson 2002; Kepler and Perelson 1998; McLean et al. 1991; McLean and Nowak 1992;
Rong et al. 2007; Ward et…
Category: