1. Yarnitsky, D.: Role of endogenous pain modulation in chronic pain mechanisms and treatment. Pain 156, S24–S31 (2015)
2. Ossipov, M.H., Morimura, K., Porreca, F.: Descending pain modulation and chronification of pain. Curr. Opin. Support Palliat. Care 8(2), 143–151 (2014)
3. O’Connell, N.E., Marston, L., Spencer, S., DeSouza, L.H., Wand, B.M.: Non-invasive brain stimulation techniques for chronic pain. Cochrane Database Syst. Rev. 4, CD008208 (2018)
4. Lefaucheur, J.P., Antal, A., Ayache, S.S., Benninger, D.H., Brunelin, J., Cogiamanian, F., et al.: Evidence-based guidelines on the therapeutic use of transcranial direct current stimulation (tDCS). Clin. Neurophysiol. 128(1), 56–92 (2017)
5. DaSilva, A.F., Volz, M.S., Bikson, M., Fregni, F.: Electrode positioning and montage in transcranial direct current stimulation. J. Vis. Exp. 51, e2744 (2011)