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:Trials were considered eligible if they satisfied the following inclusion criteria: (1) RCTs comparing RIC versus no conditioning in patients with AMI; (2) patients were treated by primary PCI or thrombolysis; (3) RIC was induced by intermittent limb ischemia–reperfusion; and (4) trials at least reported one of the following outcome measures, including enzymatic myocardial infarction size as assessed by serum peak creatine
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