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 maintenance of close nest burrows (King 1989b; Viblanc et al. 2010), greater tolerance (King 1989a; V.A. Viblanc, C. Pasquaretta, C. Sueur, R. Boonstra & F.S. Dobson, unpublished results) and less infanticide (Dobson 1990; Stevens 1998) between kin during this highly energy constraining period…
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