Dead-ball era - Wikipedia
Legends of the Dead Ball Era (1900–1919) in the Collection of Jefferson R. Burdick
Eras of ERA – The Sport Journal
A Brief History of the Baseball, Arts & Culture
Why baseball offenses are struggling and how MLB can fix it
Dead Ball Era - The Death of Ray Chapman:A Turning Point in Baseball History
Pitching: Evolution and Revolution, by John Thorn
A History of Baseball in 10 Pitches - The New York Times
Why Today's Baseball Players Don't Have the Same Skills as Old-Timers, News, Scores, Highlights, Stats, and Rumors
Eras of ERA – The Sport Journal
The game stays the same even as baseballs change