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:STAT activation is initially widespread, but must be dampened to produce an optimal number of invasive cells by stage 9 (Starz-Gaiano et al., 2008; Yoon et al., 2011; Monahan and Starz-Gaiano, 2013).
Category: