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, Ren et al. extended the results of Jadbabaie et al. (2003) and Olfati-Saber and Murray (2004) and presented some more relaxable conditions for consensus of information under dynamically changing interaction topologies (Ren & Beard, 2005).
Category: