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:…of the same functional types may be stronger than between species of different functional types, and so, patterns of species richness along gradients may be more interpretable by considering the species richness of the different functional types Peet 1978; Pausas 1994; Pausas and Austin 2001 .
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