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:…to the optic nerve in the neonatal rat induces the appearance of chromatin condensation (pyknosis) in ganglion cells (Miller and Oberdorfer, 1981; Beazley et al., 1987; Rabacchi et al., 1994a) as well as nuclear DNA fragmentation, as assessed by applying a method of in situ detection of DNA…
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