Iowa State University Veterinarian Records, RS 22/6/0/9, University Archives, Special Collections Department, Iowa State University, http://www.add.lib.iastate.edu/spcl/arch/rgrp/22-6-0-9.html
Each year, millions of dogs are taken to humane shelters across the United States. Of these dogs, it has been estimated that 15-20 million of them are euthanized. The majority of these animals are taken to shelters for some sort of behavioral problem, and by far, the most common behavioral problem found in dogs is aggressiveness. Canine aggression can be defined as an inappropriate threat, challenge, or attack by a dog against another dog, animal, or person in a given situation. It is important to realize that not all canine aggression is inappropriate-remember, one of the reasons dogs were originally domesticated was for protection. When a dog attacks visitors or family members, however, it is an inappropriate response. For all aggressive dogs, it is very important to determine the appropriateness of the behavior. Was the dog threatened, or was the aggressiveness really unprovoked?
Waelchli, Jessica L. and Draper, Donald D.
"Canine Dominance Aggression,"
Iowa State University Veterinarian: Vol. 59
, Article 10.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol59/iss2/10