Delaware State University Archives and Special Collections: Helmets Through History
Why did military personnel before WWI not wear helmets in time of war? - Quora
Leatherhead to Radio-head: The Evolution of the Football Helmet, Arts & Culture
Design and Virtual Testing of American Football Helmets–A Review
The Football Helmet timeline
Design and Virtual Testing of American Football Helmets–A Review
1920-30 Red Grange Leather Football Helmet Full Size Fine
The Evolution of Football Helmets, by Jose Diaz
The History of The Football Helmet timeline
Edmonton Seahawks added a new photo. - Edmonton Seahawks
Researchers test old-style leather helmets vs. modern ones and found leather performed as well, better in some aspects. Conclusion: Football helmets need to be softer. : r/nfl
Leatherhead to Radio-head: The Evolution of the Football Helmet, Arts & Culture
Evolution of the Football Helmet
The History of The Football Helmet timeline