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 average value of observed heterozygosity in this study is close to that obtained by Yamamoto et al. (2003) at 0.5, and is also congruent with results using isoenzymes (Huang et al. 1994; Pereira-Lorenzo et al. 2006).
Category: