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 function generating the judgment criterion y included two multiplicative combinations of the cues x1,..., x4:
 y = 4x1 + 3x2 + 2x3 + x4 + 2x1x2x3 + x2x3x4
 8.5 (1)
 We used the same items in the judgment task as in previous studies (Hoffmann et al., 2014, 2016).
Category: