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 known homologous proteins for this matrix were taken from the Database of Aligned Protein Structures (DAPS) (Murzin et al., 1995; Holm and Sander, 1996; Berman et al., 2000; Mallick et al., 2001).
Category: