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:…for regulating development of neocortical areas as well as for expansion and gyrification of the forebrain during primate evolution (Fietz et al., 2010; Hansen et al., 2010; Lui et al., 2011; Reillo et al., 2011), although this is still controversial (Hevner and Haydar, 2012; Kelava et al., 2012).
Category: