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 this work, network oscillations in theta band are investigated by evaluating the summed membrane potentials of the neurons (Pedroarena and Llinas 1997) (this is equivalent to using a summation of synaptic currents as illustrated in Fig.
Category: