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:These results were evident when comparing levels in fasting pregnant women with non-fasting [21,24-29], non-pregnant [24], or lactating women [24] or even with their own levels measured before and after breaking fast [33].
Category: