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:2009–2012) is similar to the incidence rate variation observed in multiple cohorts, in both high-income and low-income settings [3,6,15,39], and in our setting it might be a result of overall antiretroviral therapy expansion.
Category: