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:In normal cells, the principal role of Ku proteins is to mediate DNA repair, but they are also implicated in many other cellular processes, including telomere maintenance, anti-apoptosis, tumor suppression, and regulation of specific gene transcription [10-13], cell cycle control and DNA replication [14-19].
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