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:Instead of using the single fuzzless locus mutant developed mapping populations (Rong et al. 2005, 2007; Zhang et al. 2005; Guo et al. 2006; Wan et al. 2007), the common female parent line of the two F2 populations we developed combined at least two fuzzless loci (N1 and n2, and probably n3) (Turley and Kloth 2002).
Category: