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:8-kb human COX-2 cDNA containing the entire coding region of human COX-2 was inserted into the first exon of the human growth hormone gene controlled by the mouse albumin enhancer/promoter (14, 15).
Category: