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:Stimuli
The stimuli were 24 VOT continua synthesized with the Sensyn implementation of the cascade branch of the Klatt synthesizer (Klatt & Klatt, 1990) at 12-bit resolution and 10 kHz sampling rate.
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