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:Recently, loss-of function mutations in KCND3 (potassium voltage-gated channel, Shal-related subfamily, member 3) have been identified causing SCA19/22 [4, 5], whereas gain-of function mutations in KCND3 were implicated in Brugada syndrome and atrial fibrillation [6–8].
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