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:Ten Caucasian patients with grossly increased levels of N-isovalerylglycine and N-isovalerylcarnitine were diagnosed with IVA and the metadata on these cases are described in Dercksen et al. 2012.
Category: