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:Mammalian lysozymes are c-type muramidases, capable of both hydrolysis and transglycosylation (Jolles et al., 1974; Jolles and Jolles, 1984).
Category: