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:Group-specific primers for Bacteroidales order, Lactobacillus sp., Bifidobacterium sp., and Clostridium sp. were obtained from Wlodarska et al.46 and Prevotella sp. were obtained from Matsuki et al.47 Expression analysis was carried out using the Bio-Rad CFX manager 3.0 (using the DDCt method for relative normalized expression and DCt for relative expression).
Category: