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:They play an important
role in stabilizing coordination geometries, adjusting ligand donor strengths, and mediating proton transfer reactions (Span et al. 2017; Holm et al. 1996; Makris et al. 2007).
Category: