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 use a pitch difference in distinguishing the stop categories, where both vowels following aspirated and tense stops are produced with a higher pitch than those following lenis stop onsets (Jun 1996, Kang 2014, Kim 2004, Kong et al. 2011, Lee and Jongman 2012, Oh 2011, Silva 2006, Wright 2007).
Category: