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:…shows early termination of vascular elongation, while the cvl1 mutant resembles wild type, suggesting an unequal redundancy in which CVP2 plays a more significant role in PtdIns(4,5)P2 degradation and PtdIns(4)P production (Carland and Nelson, 2009; Carland et al., 1999; Carland and Nelson, 2004).
Category: