1. Centers for Medicare & Medicaid Services. National Health Expenditures 2019. Highlights. https://www.cms.gov/files/document/highlights.pdf.
2. U.S. Emergency Medical Services (EMS) Products Market Size, Share & Trends Analysis Report by Product, By End-use (Fire Department, Private Transport, Government, Hospital Owned, Volunteer), And Segment Forecasts. 2018–2025. https://www.grandviewresearch.com/industryanalysis/us-emergency-medical-services-ems-products-market.
3. Page C, Sbat M, Vazquez K, Yalcin ZD. Analysis of Emergency Medical Systems Across the World. Worcester Polytechnic Institute. 2013. http://pacdaoman.gov.om/images/pdf/research/MQFIQP2809.pdf.
4. A 6-Year Analysis of German Emergency Medical Services Helicopter Crashes