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:(2007) focus on slow EEG oscillations observed during deeper levels of desflurane-induced general anesthesia and (Liley and Bojak, 2005) model the proconvulsive properties of several volatile anesthetic agents, most modeling efforts aim at understanding the dynamical mechanisms underlying bi-phasic responses (Bojak and Liley, 2005; Hutt and Longtin, 2010; Steyn-Ross et al., 1999).
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