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:DIMM is a key regulator of expression of the neuropeptide biosynthetic enzyme, peptidylglycine-a-hydroxylating monooxygenase (PHM) (Park et al. 2008), and it promotes the differentiation of neurosecretory properties in many neurons (Hamanaka et al. 2010).
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