Here are some articles and links for your reading enjoyment!
Here are some books for those wanting to find out more:
Metal In The Mouth by Dr. Robert Cook and Dr. Hiltrud Strasser
Natural Horsemanship Explained by Robert M. Miller
The Revolution in Horsemanship by Robert M. Miller
The Natural Horse: Foundations for Natural Horsemanship by Jaime Jackson
Lyons on Horses by John Lyons and Sinclair Browning
The Seven Games of Parelli Natural Horsemanship by Pat Parelli