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:1, A and B) have been extensively reported (Rodrigues-Lima et al., 2001; Grant, 2008; Butcher and Minchin, 2012), making this enzyme an ideal intracellular candidate to investigate the consequences of nanoparticleenzyme interactions.
Category: