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 major route of excretion in mammals is via the urine (Hawkins et al. 1980; Klos and Dekant 1994; Hissink et al. 1996, 1997), and the main metabolite of p-DCB is 2,5-DCP, which is excreted both as the free substance and in conjugated forms (as sulfate or glucuronide) in the urine (Azouz et al.…
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