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:The next communication [2] considered the most general characteristics of the parameter of spa tial EEG synchronization (the average in each of the fre quency bands of the EEG’s coherence value), such as multiplicity, directedness, and reproducibility of varia tions of this parameter owing to the change of state of the subjects.
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