United States Department of Transportation. Federal Highway Administration. (2007 m. gruodžio mėn.). „Manual on Uniform Traffic Control Devices“(PDF). Federal Highway Administration. pp. 6F-33. Nuoroda tikrinta 2009-10-24.
Official Florida Driver’s Handbook 2008 (1 October 2008), Division of Driver’s Licenses, Florida Department of Highway Safety and Motor Vehicles! Web-based PDF. Chapter 4, Section 7 "Special Signs. " Channeling Devices.