United States. Federal Highway Administration. (1989). Manual on uniform traffic control devices: For streets and highways (1988 ed.). U.S. Dept. of Transportation, Federal Highway Administration For sale by the Supt. of Docs., U.S. G.P.O.
Chicago-referens (17:e uppl.)United States. Federal Highway Administration. Manual on Uniform Traffic Control Devices: For Streets and Highways. 1988 ed. Washington, D.C: U.S. Dept. of Transportation, Federal Highway Administration For sale by the Supt. of Docs., U.S. G.P.O, 1989.
MLA-referens (9:e uppl.)United States. Federal Highway Administration. Manual on Uniform Traffic Control Devices: For Streets and Highways. 1988 ed. U.S. Dept. of Transportation, Federal Highway Administration For sale by the Supt. of Docs., U.S. G.P.O, 1989.