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:A fraction of the splenocytes was cultivated in order to test the supernatants for antibody response in ELISA.(29) Only the culture supernatant from C3H/J splenocytes indicated the presence of TFbinding antibodies (data not shown).
Category: