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:Notably, a large number of propionylation sites were found not only in T. thermophilus, as previously reported (Okanishi et al. 2014), but also in another thermophilic bacterium, G. kaustophilus (Fig.
Category: