Engber, Daniel (December 21, 2015). "Concussion Lies". Slate. The Slate Group. Archived from the original on December 25, 2015. Retrieved December 26, 2015.
Engber, Daniel (December 21, 2015). "Concussion Lies". Slate. The Slate Group. Archived from the original on December 25, 2015. Retrieved December 26, 2015.