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American Academy of Dermatology: "Going to great lengths for beautiful hair: Dermatologist shares hair care tips for healthy and damaged hair," "Good Hair Care May Head Off Hair Loss," "Hair Loss: Who gets and causes," "How to stop damaging your hair," "What Causes Hair Loss?"

American Hair Loss Association: "Causes of Hair Loss."

The American Hair Loss Council: "Female Pattern Hair Loss."

FamilyDoctor.org: "Hair Loss Causes & Risk Factors."

Karthik Krishnamurthy, DO, dermatologist, director of the Cosmetic Dermatology Clinic at Montefiore Medical Center.

NHS: "Hair Loss Myth Buster."

TeensHealth: "What Causes Hair Loss."

WomensHealth.gov: "Skin and Hair Health."