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:However, the persistence of antibody responses long after malaria transmission has ceased has been reported in a non-endemic region of Brazil and in a low transmission area in Thailand, and long-lived anti-CSP antibody responses have been detected in the absence of a blood-stage infection [25, 26].
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