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:Previous research has shown that EC and EI can be significantly affected by other confounding/ independent factors such as field moisture capacity, position of the positive plant electrode and negative soil electrode, and soil/root temperature (Aubrecht et al. 2006; Dietrich et al. 2013; Postic and Claude 2016). EC increases gradually with increasing field moisture and plateaus when field moisture reaches maximum soil water capacity (Dalton 1995; Dietrich et al. 2013). The current research supports these previous results, as the EC increased and EI decreased following irrigation, regardless of treatments (Table 2). Dalton (1995) explained that a decrease in EC was caused by less effective root tissue in contact with soil medium.
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