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:There was no difference in results between the two treatment backgrounds, the presence of metformin did not affect the results, which is consistent with earlier studies of the SGLT2 inhibitors dapagliflozin [15,16] and canagliflozin [17,18].
Category: