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:Based on the alignments, phylogenetic trees were inferred using the maximum likelihood (ML) method in the PHYML program (Guindon and Gascuel 2003) in Geneious 5.3.5 package with the General-timereversible (GTR) substitution model.
Category: