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:Models on working memory have to a large extent been focused on PFC (Amit & Brunel, 1997; Durstewitz, Seamans, & Sejnowski, 2000; Lisman & Idiart, 1995), but there is also some modeling work on IT, e.g. Jensen, Idiart, and Lisman (1996), Sohal and Hasselmo (2000).
Category: