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:Although originally described as a potent stimulator of glucose-dependent insulin secretion, recent studies [1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13] have shown that the intestinal hormone GLP-1 also prevents the onset of diabetes and ameliorates existing diabetes through a mechanism that includes enhancement of beta-cell mass [16, 17, 18, 19, 20].
Category: