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:Immediately after the capture of an image, we took a second photograph of the color standard placed in the same location and photographed under the same lighting as the subjects (i.e., the “sequential method”: Higham 2006; Bergman and Beehner 2008; Dubuc et al. 2009; Stevens et al. 2009; Higham et al. 2013).
Category: