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:…People’s Republic of China
and habitat modification can affect the population dynamics of Aurelia spp. across different stages of their life cycle and thus have been proposed as possible causes of jellyfish blooms (Richardson et al., 2009; Dong et al., 2010; Purcell, 2012; Duarte et al., 2012).
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