This website is based off of the following two books which are currently in the public domain.
The Indian Sign Language
- W.P. Clark
- Publisher: University of Nebraska Press
- ISBN: 978-0803263093
Clark spent time with scouts in the 1800's.... This book has wonderful background information for the signs as well as very thorough descriptions for how to do the sign.
Indian Sign Language
- William Tomkins
- Publisher: Dover Publications
- ISBN: 978-0486220291
Much of Tomkins book is based off of the book by Clark. The advantage of it though is that it does contain illustrations to help you in figuring out the sign.
Additional reading that may be of interest.
Sign Talk of the Cheyenne IndiansIndian Signals and Sign Language