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:The basic T-tag suturing method, which had been first described in 2002 [20], was further developed during an Inventorama devoted solely to suturing; improvements to the articulating grasper resulted from the NOTES Toolbox event.
Category: