1. Bochove, G. G. (1996).Twinlay, a new concept for porous asphalt. Proceedings of 1st Eurasphalt & Eurobitume Congress, Strasbourg (pp. E&E.7.187).
2. Bureau of Transportation Statistics. (2002).National Transportation Statistics 2002. Retrieved from http://www.bts.gov/publications/national_transportation_statistics/2002/index.html
3. Federal Highway Administration. (2000).Highway Statistics 1999. Retrieved from http://www.fhwa.dot.gov/ohim/hs99/
4. East Nippon Expressway Co. Ltd. (2011).NEXCO testing standard. Chapter 3 asphalt, pp. 1–4.