The definitive description of Schutzhund training in the first 50 years of the sport is Col. Konrad Most's "Dog Training: A Manual", 1910. By modern standards, Most's training is very harsh and possibly abusive. Despite this, it is also structured, consistent, and in many ways conforms to more recent ideas on learning theory. Over time, the more brutal techniques fell out of use and few trainers still follow Most's program. In 1981, Helmut Raiser published "Der Schutzhund", which radically changed Schutzhund protection training. In the US, the next great change in Schutzhund training is marked by the 1991 publication of "Schutzhund Theory & Training Methods" by Susan Barwig and Stewart Hilliard. Dr. Dietmar Schellenberg presents a remarkably comprehensive guide with detailed, step-by-step instructions on Schutzhund training and theory in his 1981 book "Top Working Dogs, A Schutzhund Training Manual".