Hypomagnesemia 
Wikipedia article discusses symptoms, signs, causes, and treatment.
http://en.wikipedia.org/wiki/HypomagnesemiaeMedicine: Hypomagnesemia
Clinical article offers definition, effected systems, physical symptoms, causes, lab studies, and treatment.
http://www.emedicine.com/emerg/topic274.htm
eMedicine: Hypomagnesemia
Anastasios K Konstantakos, MD discusses the importance of this mineral to system function, physical symptoms, tests, medical care, and medications.
http://www.emedicine.com/ped/topic1122.htm
Hypomagnesemia
Journal of Family Practice describes possible causes of this mineral deficiency, associated diseases, and risk factors.
http://www.jfponline.com/Pages.asp?AID=1871&UID=
Magnesium Deficiencies
Reviews mitral valve prolapse as a symptom of a magnesium deficiency as well as anxiety and psychiatric disorders, asthma, fibromyalgia, chronic fatigue syndrome and many other disorders.
http://www.ctds.info/5_13_magnesium.html
The Importance of Magnesium to Human Nutrition
HealthWorld Online discusses this important mineral, the symptoms of deficiency, diagnosis of deficiency, oral and injectable treatment, and supplementation for various disorders.
http://www.healthy.net/asp/templates/article.asp?PageType=Article&ID=541
Magnesium: Coming of Age
Explains the importance of this mineral in hypertension and heart disease. Includes how it effects the body, who is at risk hypomagnesemia, and replacement strategies.
http://www.mgwater.com/harvard.shtml
