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:In a recent elegant study performed on choroid plexuses obtained from neonatal and adult rats and in an in vitro model of the blood-CSF barrier, the active transport of Mn through the basolateral membrane of epithelial cells was shown to be partially saturable, unidirectional (from the blood to the CSF) and influenced by prolonged exposure of both Mn and Ca (Schmitt et al., 2011).
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