Supplemental material, Supplemental Material4 for Multicentre assessment of motor and sensory evoked potentials in multiple sclerosis: reliability and implications for clinical trials by Martin Hardmeier, François Jacques, Philipp Albrecht, Habib Bousleiman, Christian Schindler, Letizia Leocani and Peter Fuhr in Multiple Sclerosis Journal – Experimental, Translational and Clinical</p