Ylinen, Jari, Riku Nikander, Matti Nykänen, Hannu Kautiainen, and Arja Häkkinen. 2010. “Effect of Neck Exercises on Cervicogenic Headache: A Randomized Controlled Trial”. Journal of Rehabilitation Medicine 42 (4):344-49. https://doi.org/10.2340/16501977-0527.