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 observation corroborates findings from Olver & Jonker (1997) and Nir et al. (1994b), who also showed a direct relationship between the particle size of the ingredients or diet and the morphology of the digestive system.
Category: