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:This finding contrasts with telomere attrition that is observed in human cells with undetectable telomerase activity (our data) and in mouse cells (Gu et al., 2012) that display significantly lower telomerase activity compared to cancer cells.
Category: