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:Additional support for Öhman’s view comes from electromyographic and neuroimaging studies of unconscious processing of masked facial expressions (Morris et al., 1998; Whalen et al., 1998; Dimberg, 2000; Dimberg et al., 2000).
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