Effect of nitrous oxide on myogenic motor potentials evoked by a six pulse train of transcranial electrical stimuli: a possible monitor for aortic surgery. - van Dongen,E.P.; Beck,H.AT.; Schepens,M.A.; Morshuis,W.J.; de Boer,A.; Aarts,L.P.; Boezeman,E.H. (Br J Anaesth, 1999)