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:This prompts speculation that non-neuronal defects observed following exposure to chemical AChE inhibitors reflect off-target effects (Behra et al., 2004) or that in vitro morphogenetic functions of AChE are irrelevant/redundant in vivo (Cousin et al., 2005; Johnson et al., 2008b).
Category: