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:When we compare the sponge species composition of the caves studied with that of other Mediterranean caves (e.g. Marseilles caves, Pouliquen, 1972; Harmelin & Vacelet, 1997; and Migtigliano cave, Balduzzi et al., 1989), we ¬¨¬¢nd that the number of species in common is generally low, and decreases‚Äö√Ñ¬∂
Category: