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:Then, the SVM, which has been proven to have high efficiency in classifying the high-dimensional feature in previous studies (Lilleberg et al. 2015, Zhang et al. 2015b), was applied to our proposed model to identify the urban land use types in the TAZs.
Category: