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:…that various mechanisms such as telomere shortening, histone modification, DNA methylation and miRNA expression affect the proliferation and differentiation of MSCs, resulting in cell senescence (Bonab et al., 2006; Noer et al., 2006; Wagner et al., 2008; Zhang et al.,
2008; Bork et al., 2010).
Category: