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:Five of 8 subscales of this previously validated instrument were used: (1) limitations in physical activities because of physical or emotional problems; (2) limitations in usual role activities because of physical health problems; (3) limitations in usual role activities because of emotional health problems; (4) general health perceptions; and (5) general mental health.
Category: