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 explanation for such finding is not clear, since the pellet dissolves within the proventriculus (Nir et al., 1994c), and thus it was not expected that physical form of the diet would have any effect in this portion of the gastrintestinal tract.
Category: