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 fiber length distribution and coarseness were measured using a fiber quality analyzer (FQA, OpTest Equipment Inc., Hawkesbury, Canada) with an average of 5,000 fibers analyzed as previously described (Ju et al. 2013b).
Category: