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:Activation of both the Jak/STAT and MEK/ERK signalling pathways has been implicated on IFN-γ-induced iNOS expression (Blanchette et al., 2003; Park et al., 2005; Shen et al., 2005).
Category: