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:By contrast, the activation of epithelial cells and fibroblasts by LL-37 apparently does not involve a sterospecific interaction, as the D-enantiomer and L-enantiomer of LL-37 exhibit comparable activities (Tomasinsig et al., 2008; von Haussen et al., 2008).
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