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:Furthermore, we previously showed that the increase of eIF2a phosphorylation induced by Sal 003, a specific inhibitor of its phosphatase, can elevate BACE1 protein levels in 6-month-old 5XFAD mice, which have not yet showed BACE1 upregulation consistent with only marginal changes in eIF2a phosphorylation [3].
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