Naka, Asami, et al. “Does Transcutaneous Electrical Nerve Stimulation (TENS) Have a Clinically Relevant Analgesic Effect on Different Pain Conditions? A Literature Review”. European Journal of Translational Myology, vol. 23, no. 3, July 2013, pp. 95-104, https://doi.org/10.4081/ejtm.2013.1779.