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:If medical evaluation reveals systemic lymphoma, treatment of the ocular disease is secondary to systemic treatment (usually chemotherapy).(1-30) The effectiveness of EBRT for the treatment of lymphoma of the eye and its adnexa has been widely documented.
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