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:…during the La Niña phase of the El Niño Southern Oscillation (ENSO), have the most direct influence, with Atlantic Ocean SSTs perhaps having an indirect influence through dynamic effects on the atmospheric general circulation (Cook et al. 2011; Kushnir et al. 2010; McCrary and Randall 2010).
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