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:However, conflicting results from studies in murine models have been published regarding the role of mTOR for the development of embryonic and extraembryonic tissues (Gangloff et al., 2004; Shiota et al., 2006; Wullschleger et al., 2006; Guertin and Sabatini, 2007; Yang and Guan, 2007; Rosner et al., 2008).
Category: