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:We present an implementation of Yager’s [32, 33] idea, mainly using Kacprzyk and Yager’s [7], and Kacprzyk, Yager and Zadro ny's [8, 9] extensions.
Category: