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:…difference between aspirated and lenis is merging for younger speakers, resulting in a two-way VOT contrast: aspirated & lenis (long VOT) vs. tense (short VOT) (Choi 2002, Kang and Guion 2008, Kang 2014, Kim 2000, Kim 2004, Kong et al. 2011, Lee and Jongman 2012, Oh 2011, Silva 2006, Wright 2007).
Category: