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:2D), associated with the unchanged total creatine content previously reported in aged muscles by other investigators (Ermini & Verzar, 1968; Dudley & Fleck, 1984; Conley
et al., 2000), clearly demonstrates that the decrease in energy-supply elasticity in aged rats arises from alteration(s) located…
Category: