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:A Phylogenetic Approach (9), and were provided with limited supplementary and/or review reading from Bioinformatics: A Practical Guide to the Analysis of Genes & Proteins (1), Bioinformatics for Dummies (5), Biology (4), and Brock Biology of Microorganisms (7).
Category: