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:These results are similar to those of Nilsson et al. (1994), who suggested that the abundance and species richness of Dytiscidae were correlated with the amount and complexity of vegetation, as well as shore slope in a number of Swedish lakes.
Category: