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:Cross-talk between JA and SA signalling has been described in response to various attackers (Beckers and Spoel, 2006; Stout et al., 2006; Koornneef and Pieterse, 2008).
Category: