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:Third, we used a meta-analysis technique to assemble the results of eligible studies, and the pooled results were presented in the format of quantitative data; whereas in the systematic review by Jiang et al, they only described the previous relevant studies and did not give a quantitative analysis for these studies.(13) Although studies comparing between ACDF and ACCF have been done, the optimal approach that provides better clinical effects in the treatment of CSM remains controversial.
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