"Speed Limit 55: Is It Achievable?" Report to the Congress by the Comptroller General of the United States. Washington, D.C.: General Accounting Office, February 14, 1977. Retrieved from https://www.gao.gov/assets/120/118193.pdf (页面存档备份,存于互联网档案馆)
"Speed Limit 55: Is It Achievable?" Report to the Congress by the Comptroller General of the United States. Washington, D.C.: General Accounting Office, February 14, 1977. Retrieved from https://www.gao.gov/assets/120/118193.pdf (页面存档备份,存于互联网档案馆)