1. Second IMO GHG Study 2009;Buhaug,2009
2. Interview with Systems Engineer;Cushing,2014
3. Department of Defense, 2008. Global Positioning System Standard Positioning Service Performance Standard, 4th Ed.
4. Enginei, Royston Diesel Power. 〈http://www.enginei.co.uk/faqs.html〉 (last accessed June 2015).
5. Federal Aviation Administration (FAA) GPS Product Team, Global Positioning System (GPS) Standard Positioning Service (SPS) Performance Analysis Report, July 2014. Report #68, FAA.