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 female skeletomuscular system
Flightlessness of females of Geometridae is usually linked with a specific set of ecological traits (Snäll et al. 2007; Wahlberg et al. 2010) and also reflects some general trends of flightlessness in pterygote insects (Roff 1986, 1990; Wagner and Liebherr 1992).
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