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:Morphometrical analysis for villous height, crypt depth, villous width, epithelial surface area, and villous compartment volume was done as described elsewhere [18], but only the first 2 measurements were taken for biopsy samples obtained after baseline.
Category: