Hein E, Nowak M, Kiess O, Biermann T, Bayerlein K, Kornhuber J, Kraus T. Auricular transcutaneous electrical nerve stimulation in depressed patients: a randomized controlled pilot study. Journal of Neural Transmission [Internet]. 2013;120(5):821 - 827. http://link.springer.com/10.1007/s00702-012-0908-6