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:The degree of coronary stenosis was classified from 5 to 0 as follows: 5 for total occlusion, 4 for 75–99 % stenosis, 3 for 50–74 % stenosis, 2 for 25–49 % stenosis, 1 for up to 24 % stenosis, and 0 for no atherosclerosis [4].
Category: