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:On the basis of this Pinzur grouping [1, 15] and PEDIS criteria [5, 6, 20] a complication analysis was performed with the goal of evaluating those patients at risk who do not qualify for internal corrective arthrodesis.
Category: