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 28-item Dissociative Experiences Scale–II (DES-II) measures the frequency of psychoform dissociative experiences on a 0–100 scale (Bernstein & Putnam, 1986; Carlson & Putnam, 1993).
Category: