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:PAR has been described using the image of a spiral (Williamson et al., 2004), and various authors report the suitability of the application of this method to the management of change within organizations (Coghlan and Casey, 2001; Coyer et al., 2007; Kelly and Simpson 2001).
Category: