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:The methods of animal training, stimulus delivery, and physiological recording have been described previously (Malone et al. 2002, 2007, 2010, 2014; Scott et al. 2007, 2009, 2011).
Category: