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:Assuming the well-known Kronecker correlation structure [10–13] we can decompose H as H = R 1 2HwS 1 2 (2) where R and S are the receive and transmit correlation matrices respectively, satisfying tr (R) = Nr and tr (S) = Nt, and the elements of Hw are i.
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