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:Thus, the authors focus on the tf ⋅ idf value (term frequency times inverse document frequency) [20, 21] used as a feature selection value when representing documents as multidimensional vectors, then use this as a word weight and apply it to Profit Sharing.
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