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 Hutt and Longtin (2010) chose pi=pe, reflecting equal affinity of propofol for GABAA receptors located on cortical inhibitory and pyramidal neurons, we relax this assumption, thereby accounting for the possibly differential affinity of propofol for different neuron types.
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