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:Desaturation/elongation of EFAs occur mainly in liver microsomes, but active EFA metabolism has been also found in other tissues, such as kidney [3] and testis [4], and we demonstrated that even heart microsomes have the ability to desaturate LA and to synthesize arachidonic acid (AA) to satisfy partially tissue needs for eicosanoid production [5].
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