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:Assessing Risk of Bias
 Critical appraisal of the studies, based on the Cochrane Risk of Bias Tool (Higgins and Green 2009), involved assessing whether there was an adequate method of sequence generation, allocation concealment, blinding of assessors, satisfactory treatment of attrition, including‚Ä¶
Category: