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 RDCs have been successfully applied in the refinement of protein structures (Stauffer et al. 2002), nucleic acids (McCallum and Pardi 2003) and protein– RNA complexes (Bayer et al. 1999).
Category: