Kammer, T., Beck, S., Thielscher A, Laubis-Herrmann, U., & Topka, H. (2001). Motor thresholds in humans: a transcranial magnetic stimulation study comparing different pulse waveforms, current directions and stimulator types. Clinical Neurophysiology, 112, 250-258. Retrieved from http://www.sciencedirect.com/science?_ob=ArticleURL_udi=B6VNP-429XWRH-4_user=29041_coverDate=022F282F2001_rdoc=4_fmt=summary_orig=browse_srch=23toc2361842320012399887999723227790!_cdi=6184_sort=d_docanchor=_acct=C000003178_version=1_ur.