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^Planning and Research Division (March 1990). General Highway Map Craighead County, Arkansas(PDF) (Map). 1:63500. Little Rock: Arkansas State Highway and Transportation Department. Retrieved April 6, 2011.
^Transportation Planning and Policy Division (September 17, 2021). State Highway Route and Section Map, Washington County, Arkansas(PDF) (Map). 1:62,500. Cartography by GIS Section. Little Rock: Arkansas Department of Transportation. Retrieved December 21, 2021.
^Special Committee on U.S. Route Numbering (November 20, 2014). "Report to SCOH"(PDF) (Report). Washington, DC: American Association of State Highway and Transportation Officials. p. 1. Archived(PDF) from the original on January 28, 2019. Retrieved December 21, 2021.
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^Special Committee on U.S. Route Numbering (May 21, 2019). "2019 Spring Meeting Report to the Council on Highways and Streets"(PDF) (Report). Washington, DC: American Association of State Highway and Transportation Officials. p. 1. Archived(PDF) from the original on July 12, 2019. Retrieved December 18, 2021.
^Transportation Planning and Policy Division GIS Section (September 17, 2021). State Highway Route and Section Map, Union County, Arkansas(PDF) (Map). 1:62,500. Little Rock: Arkansas Department of Transportation. Retrieved December 18, 2021.
^Special Committee on U.S. Route Numbering (May 22, 2018). "2018 Spring Meeting Report to the Council on Highways and Streets"(PDF) (Report). Washington, DC: American Association of State Highway and Transportation Officials. pp. 1–2. Archived(PDF) from the original on June 3, 2019. Retrieved December 17, 2021.
^"Minutes of the Meeting"(PDF). Arkansas State Highway Commission. September 2000. pp. 922–923. Retrieved December 4, 2016.