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:Finally, the role of MMPs in fibrogenesis is complicated by their apparent role in both the resolution of liver fibrosis, in which MMPs promote ECM degradation, and their role in clearance of fibroblastic HSCs (9, 22, 23, 41).
Category: