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:3 To this end, the proposed method is compared with several recommendation methods including User-based CF (UCF), Item-based CF (ICF) [51], SlopeOne [52], SVD++ [53], TARS [12], SoRec [31], SoReg [54], TrustMF [22], SocialMF [28], TrustSVD [25], IPG [26], CETrust [21], and 2DGC [55].
Category: