Usami K, Kawai K, Sonoo M, Saito N. Scalp-Recorded Evoked Potentials as a Marker for Afferent Nerve Impulse in Clinical Vagus Nerve Stimulation. Brain Stimulation [Internet]. 2013;6(4):615 - 623. http://linkinghub.elsevier.com/retrieve/pii/S1935861X12001611