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:McCartney and Lessios (2004) have suggested that E. lucunter, because it is found in high point population densities almost exclusively in a high energy narrow intertidal zone, is likely to spawn under conditions of high density of mixed sperm.
Category: