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:…(Buttle et al., 2006), and there are many examples of studies examining the adoption of mobile technology and mobile services (Balocco et al., 2009; Kim and Garrison, 2009; Liang et al., 2007), to the best of the authors’ knowledge, this is the first study to combine these two perspectives in an…
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