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:intergenic and upstream of chorion genes (Delidakis and Kafatos, 1989; Heck and Spradling, 1990; Orr-Weaver and Spradling, 1986).
Category: