Letter: Guidelines for the use of Electrophysiological Monitoring for Surgery of the Human Spinal Column and Spinal Cord. Issue 2 (August 2018) - Sala, Francesco; Skinner, Stanley A; Arle, Jeffrey E; Constantini, Shlomi; Deletis, Vedran; Kothbauer, Karl F; MacDonald, David B; Shils, Jay; Soto, Francisco; Szelenyi, Andrea