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:In a related approach, Daunizeau et al. (2009)) replaced the standard dipole source— used in neural mass models — with the principal Fourier mode of a neural field, for the particular case of exponentially decaying synaptic density over the cortical surface.
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