The Era of the Industrial Athlete
Evolution of Football Helmets
The History of The Football Helmet timeline
Ace Parker, Pro Football Hall of Famer From Leather-Helmet Days, Dies at 101 - The New York Times
Applied Sciences, Free Full-Text
The Football Helmet timeline
The Evolution of Football Helmets, by Jose Diaz
Leatherhead to Radio-head: The Evolution of the Football Helmet, Arts & Culture
Design and Virtual Testing of American Football Helmets–A Review
Impact test comparisons of 20th and 21st century American football helmets in: Journal of Neurosurgery Volume 116 Issue 1 (2012) Journals