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:These properties have been noticed by others who used ̂κ in place of ̂ (Friedman 1989; Brown et al. 1999), and they can be exploited to reduce the computation time for regularized discriminant analysis in high-dimensional settings (Hastie and Tibshirani 2004).
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