Bullough, John D., Nicholas P. Skinner, and Conan P. O’Rourke. “Legibility of Urban Highway Traffic Signs Using New Retroreflective Materials”. Transport 25, no. 3 (September 30, 2010): 229-236. Accessed November 26, 2024. https://mma.vgtu.lt/index.php/Transport/article/view/5784.