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:There exist some other techniques for controlling multivariate processes, such as multi-way PCA [7] (Louwerse and Smilde, 2000) and multi-way PLS [8] (Nomikos and MacGregor, 1995), the application of them is to reducing the dimensionality of the variable space for a multivariate process.
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