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:…to treatment (Zolnierek & Dimatteo, 2009), uptake of cancer screening (Carcaise-Edinboro & Bradley, 2008), improved blood pressure control in hypertensive patients (Orth, Stiles, Scherwitz, Hennrikus, & Vallbona, 1987), and reductions in the risk of serious medical error (Kuzel et al., 2004).
Category: