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:GFP fluorescence of COS7 cells expressing GFP-COQ7 and the deletion mutants GFPCOQ7(11-217), lacking amino acids 1-10, and GFP-COQ7(30-217), lacking amino acids 1-29.
Category: