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 OT dosage used in this study is 4 IU lower than the dose used in other studies demonstrating significant effects of OT on psychological variables (Kosfeld et al., 2005; Guastella et al., 2009; Ditzen et al., 2009).
Category: