RT Journal Article SR Electronic T1 Cluster Headache: Mechanisms and Management JF British Journal of Ophthalmology JO Br J Ophthalmol FD BMJ Publishing Group Ltd. SP 872 OP 872 DO 10.1136/bjo.65.12.872 VO 65 IS 12 A1 C. J. Earl YR 1981 UL http://bjo.bmj.com/content/65/12/872.1.abstract AB