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:The GFP-hyg was amplified from pIGPAPA [45], and the 39 flanking region of the MYT1 gene was amplified by primer pair MYT1-3F/MYT1-3R.
Category: