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:In addition, they are in keeping with reports that Ser19 phosphorylation is low in swine carotid arteries relaxed with forskolin (Meeks et al. 2008) as well as in a-toxin permeabilized mouse tail arteries relaxed with urocortin and cAMP (Lubomirov et al. 2006).
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