The Football Helmet timeline
Edmonton Seahawks added a new photo. - Edmonton Seahawks
Design and Virtual Testing of American Football Helmets–A Review
The Evolution of Football Helmets
Design and Virtual Testing of American Football Helmets–A Review
History of the football helmet - Wikipedia
Protected Development: A Century of Football-Helmet Innovation – Indianapolis Monthly
Vintage 1930s FOOTBALL Photo Picture LEATHERHEAD HELMET Era - Denmark
Check Out the Football Helmets Of Yesteryear
The History of the Football Helmet - Brain Injury Law Center
The History of The Football Helmet timeline
Old School: Leatherhead Football Helmets Worked As Well As Modern Ones
A Short History of American Football Helmets - HubPages
Delaware State University Archives and Special Collections: Helmets Through History