Facci, L.M., Nowotny, J.P., Tormem, F. and Trevisani, V.F.M. 2011. Effects of transcutaneous electrical nerve stimulation (TENS) and interferential currents (IFC) in patients with nonspecific chronic low back pain: randomized clinical trial. São Paulo Medical Journal. 129, 4 (Jul. 2011), 206–216.