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:Demonstration of intrathecal immunoglobulin and antibody synthesis are powerful tools for diagnosis of neurological disorders, as has been shown for multiple sclerosis and several infectious diseases of the CNS (Reiber and Lange, 1991; Felgenhauer and Reiber, 1992; Andersson et al., 1994; Tumani et al., 1995; Reiber and Peter, 2001).
Category: