Shannon M. Bravo Petersen and Vassilios G. Vardaxis. The flexion – rotation test performed actively and passively: a comparison of range of motion in patients with cervicogenic headache J Man Manip Ther. 2015 May; 23(2): 61–67. Ogince M1, Hall T, Robinson K, Blackmore AM. The diagnostic validity of the cervical flexion-rotation test in C1/2-related cervicogenic headache. Man Ther. 2007 Aug; 12(3): 256—62. Epub 2006 Nov 16.