American Academy of Family Physicians
Aafp: Assessment and Management of Concussion in Sports
This article from the American Academy of Family Physicians provides a good description of what a concussion is and how it should be treated.
Healthline Media
Medical News Today: Articles: Neurology: What Is Concussion?
Learn the causes, symptoms, grades, and treatments of concussions. Detailed information about diagnosing a concussion and the Glasgow Coma Scale is included.