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:While the maximum likelihood solution is ill-posed in infinite dimensions, Sriperumbudur et al. (2017) have demonstrated that it is possible to fit the KEF via score matching (Hyvärinen, 2005), which entails solving a linear system of size n × d, where n is the number of samples and d is the…
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