1. Anderson D, Fuller-Rowell T (1999) The ionosphere, space environment topics (SE-14) [Online]. Available at: http://www.swpc.noaa.gov/info/Iono.pdf . Accessed 10 Jan 2010
2. Appleton EV (1932) Wireless studies of the ionosphere. Proc Wirel Sect Inst Electr Eng 7(21):257–265
3. Balanis CA (2005) Antenna theory—analysis and design, 3rd edn [Online]. Available at: http://knovel.com/web/portal/browse/display?_EXT_KNOVEL_DISPLAY_bookid=1955&VerticalID=0 . Accessed 7 Sept 2009
4. Bassiri S, Hajj GA (1993) Higher-order ionospheric effects on the global positioning system observables and means of modeling them. Manuscr Geod 18:280–289
5. Bilitza D, Reinisch BW (2008) International Reference Ionosphere 2007: improvements and new parameters. Adv Space Res 42(4):599–609