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:Molecular, anatomical and behavioural characteristics of GR-i mice
As previously reported (Froger et al. 2004 ; Holsboer & Barden, 1996 ; Pepin et al. 1992), genome incorporation of the transgene encoding GR antisense RNA downregulated GR expression in GR-i mice.
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