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 our model, we did this by varying the linear response (gsac) of this current in a series of simulations from 0 to 250 (S/Fs), which corresponds up to two times the published values for these types of currents (15, 45), to account for other possible similar current sources and establish potential trends.
Category: