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:Since no such differences could be detected in the expression of the endogenous ctl(VI) gene by in situ hybridization and immunohistochemistry (Marvulli et al., 1996), it should be concluded that the 7.
Category: