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:S3B) and, together, these observations are consistent with a previously defined role for Pk in the clustering of Vang (Bastock et al., 2003; Cho et al., 2015; Strutt and Strutt, 2007).
Category: