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:The second group (Ah-type neurons) displays broader action potentials than Atype neurons, exhibits a small hump on the falling phase of the action potential, and have axons that conduct in the slow myelinated fiber range (Stansfeld and Wallis 1985, Li and Schild 2007b).
Category: