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:Although there were significant structural and functional differences among hydro-geomorphic habitats, the lack of temporal replication in the present study means that the
results need to be interpreted with caution inherent in studies that lack temporal replication (Oksanen, 2001).
Category: