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:Thus, the most plausible interpretation of the results obtained in the present work is that the nuclear gene activity plays an important role in the phenotypic manifestation of the MERRF mutation (Lertrit et al., 1992), as has been shown for other disease-causing mtDNA mutations (Harding et al.
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