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:CVL1 and CVP2 dephosphorylate PtdIns(4,5)P2 and, by acting in opposition to
PIP-kinases (Carland and Nelson, 2009; Carland and Nelson, 2004), help tightly regulate the levels of PtdIns(4,5)P2 necessary for initiation of endocytosis during PIN1 trafficking (Rodriguez-Villalon et al., 2015; Tejos et…
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