Date Nails by Jeff Oaks - A super collection of Date Nail History and awesome reference material written by Jeff Oaks.
Date Nails and Railroad Tie Preservation - Volume I by Jeff Oaks. Great information - Also found on Jeff's site and Nailhunter.com
Date Nails and Railroad Tie Preservation - Volume II by Jeff Oaks. Great information - Also found on Jeff's site and Nailhunter.com
Date Nails and Railroad Tie Preservation - Volume III by Jeff Oaks. Great information - Also found on Jeff's site and Nailhunter.com
Nailhunter.com - Some of the best reference material you will find is located on Nailhunter.com - by Scott Weed.
Be sure to check the Home Page for this site for all the pictorial views of date nails.
Dating Nails on the Atchison, Topeka and Sante Fe Railway taken from a letter by R.H. Beeder to the Otero County Historical Society
Wikipedia - Date Nails
Steel Rails and American Roalroads 1867 by Jeremy Atack and Jan K. Brueckner