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 lower abundance of fish at impacted reaches detected in our study agrees with the results of other authors, who in some cases found four times higher biomass at control reaches (Kube cka et al. 1997; Almod ovar & Nicola 1999).
Category: