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:During RNA degradation, 28S rRNA degrades faster than 18S rRNA, and therefore, the appearance of higher 28S rRNA peaks compared to 18S peaks has been recognized as a sign of preserved RNA quality (Schroeder et al. 2006).
Category: