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:…tool which provides enhanced capabilities for peptide sequencing directly from samples such as nervous tissues or even single cells of invertebrates, including those of insects (e.g., Yew et al., 2003; Billimoria et al., 2005; Neupert and Predel, 2005; Nachman et al., 2006; Wegener et al., 2006).
Category: