Nissen, Judith B., Henrik Egekvist, Peter Bjerring, and Knud Kragballe. “Effect of Intradermal Injection of Methionine-Enkephalin on Human Skin”. Acta Dermato-Venereologica 79, no. 1 (January 1, 1999): 23–26. Accessed April 26, 2026. https://medicaljournalssweden.se/actadv/article/view/14163.