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:As reproduction appears the key trait maximizing fitness (Viblanc et al. 2010), we predicted that greater allocations into reproduction should be made in the presence of greater number of kin, either due to a positive effect of kin numbers on energy income, or if more female kin provide a safer environment for raising the young.
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