3. Hallucinogenic Treatment of Neuro-Vascular Headaches
Outstanding results have been seen by many cluster headache sufferers and although clusters have been the major focus, early and current "research" shows equally effective results for related vascular headaches.
http://www.clusterbusters.com/

4. WebMD Migraines and Headaches Center - Find migraine and headache information including triggers ...
WebMD Migraines and Headaches Center - Find migraine and headache information including triggers and treatments. Approximately 45 million Americans suffer from chronic headaches, and of them, 28 million suffer from migraines.
http://www.webmd.com/migraines-headaches/default.htm

5. MedlinePlus: Headache
(American Headache Society, Committee on Headache Education) Headaches: Headaches can have many causes, but serious causes of headaches are rare. The most common type of headache is a tension headache.
http://www.nlm.nih.gov/medlineplus/headache.html