1. Tang N, Stein J, Hsia RY, Maselli JH, Gonzales R (2010) Trends and characteristics of US emergency department visits, 1997–2007. JAMA 304:664–670
2. Fischer AJ, O’Halloran P, Littlejohns P, Kennedy A, Buston G (2000) Ambulance economics. J Public Health Med 22:413–421
3. Wringley H, George S, Smith H, Snooks H, Glasper A, Thomas E (2002) Trends in demand for emergency ambulance services in Wiltshire over nine years: observational study. BMJ 324:646–647
4. Lowthian JA, Jolley DJ, Curtis AJ, Currell A, Cameron PA, Stoelwinder JU, McNeil J (2011) The challenges of population ageing: accelerating demand for emergence ambulance services by older patients, 1995–2015. MJA 194:574–578
5. Fire and Disaster Management Agency of the Ministry of Internal Affairs and Communications, Japan. (2011) Annual Report on Rescue operations; First-aid. The 2011 edition. Fire and Disaster Management Agency of the Ministry of Internal Affairs and Communications, Japan. Tokyo, Japan. ( http://www.fdma.go.jp/en/ . Accessed 3 Dec, 2012.)