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:However, a few studies reported that Brn4 and Oct6 interact not only with the octamer sequence but also with AT-rich sequences that lack the ATGC site recognized by POUS (15, 45, 66).
Category: