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:Mitochondrial mechanisms have been implicated in the pathogenesis and progression of amyotrophic lateral sclerosis (ALS; Wong et al., 1995; Bendotti et al., 2001; Beal, 2005; Martin, 2010a; Reddy and Reddy, 2011; Muyderman and Chen, 2014).
Category: