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 strain shows accelerated age-related hearing loss (Henry and Chole, 1980; Hunter and Willott, 1987; Mikaelian, 1979; Spongr et al., 1997; Willott, 1986). This can begin as early as 2 months of age, although audiometric evidence of hearing loss appears w3 months. Taberner and Liberman (2005) compared auditory nerve fiber responses between C57bl/6 (w4 month) and CBA strains (age between 2 and 4 months) and found no differences in spontaneous rates, tuning curves, rate versus level functions, dynamic range, response adaptation, phase-locking, and the relation between spontaneous rate and response properties.
Category: