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:This occupational social class measure has been previously used to investigate socioeconomic inequalities in mortality, cardiovascular disease, disability, and trends in inequalities in all-cause and coronary disease in this cohort [18,22,23], and other studies [24-28].
Category: