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:Up to now, no role for FGF signaling in aVE induction has been described, however, Fgf8b was found to be important for the correct positioning of the aVE (Guo and Li, 2007).
Category: