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:Rabbits were divided into three groups: group 1 (sham), animals were anesthetized for 40 min, but no other intervention was performed prior to blood-draw; group 2 (rIPC), remote ischemic preconditioning was induced through four cycles of 5 min of hindlimb ischemia (via a tourniquet), followed by 5 min of reperfusion as previously described [2]; and group 3, electroacupuncture (EA) was applied bilaterally with one needle at the P6 Neiguan point (located on the medial forelimb 1/6 the length of the line from the wrist to the elbow between the radius and ulna) and the other needle at P5 (Jianshi point).
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