1. Federal Highway Administration, Our Nation’s Highways – selected facts and figures. Publication No. FHWA-PL-01-1012. Office of Highway Information Management; 2000.
2. US Environmental Protection Agency. Evaluation of ecological impacts from Highway Development, EPA 300-B-94-006, Washington, DC; 1994.
3. The impact of environmental assessment: second environmental assessment review of projects;World Bank,1996
4. Beeldens A. An environmentally friendly solution for air purification and self cleaning effect: the application of TiO2 as photocatalyst in concrete. In: Proceedings of transport research arena Europe, TRA, Göteborg, Sweden; 2006.
5. Performance of ultraviolet photocatalytic oxidation for indoor air cleaning applications;Hodgson;Indoor Air,2007