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:Moreover, some comprehensive databases, such as Phytozome, GreenPhylDB, and PLAZA supply bioinformatic utilities for TF investigation (Rouard et al. 2011; Goodstein et al. 2012; Proost et al. 2015).
Category: