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:Multi-conformation continuum electrostatics (MCCE) (Alexov 2003; Alexov and Gunner 1997; Georgescu et al. 2002) method was used to calculate the charges of the ionizable groups.
Category: