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:For fitting, all data were normalized for imaging-related photobleaching during postbleach time lapse (Walczak et al., 2010), and the average of all experimental traces from the wild type or synthetic double mutant was fit with a single exponential curve.
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