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:The SAS theory is supported by studies conducted separately in the auditory (Hari, 1995; Hari and Kiesilä, 1996; Helenius, Uutela, & Hari, 1999) and visual (Hari, Renvall, & Tanskanen, 2001; Hari, Valta, & Uutela, 1999) modalities.
Category: