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:Left renal glucose utilization and splanchnic glucose utilization (utilization) were calculated using the formula
 utilization 5 FEGlc 3 3Glc4a 3 R1H2PF (4)
 where R(H)PF equals either unilateral renal plasma flow or hepatic plasma flow.
Category: