1. Allain DJ, Mitchell CN (2008) Ionospheric delay corrections for single-frequency GPS receivers over Europe using tomographic mapping. GPS Solut. doi: 10.1007/s10291-008-0107-y
2. Angrisano A, Gaglione S, Gioia C, Massaro M, Robustelli U (2013) Assessment of NeQuick ionospheric model for Galileo single-frequency users. Acta Geophys. doi: 10.2478/s11600-013-0116-2
3. Covington AE (1969) Solar Radio Emission at 10.7 cm, 1947–1968. J Roy Astron Soc Can 63/3:125–132
4. DOD SPS, Department of Defense USA (2008) Global positioning system standard positioning service performance standard, 4th edn. http://www.gps.gov/technical/ps/2008-SPS-performance-standard . Accessed 6 Jan 2012
5. EUROCONTROL Robert E (2012) Eurocontrol space weather activities. Space Weather Workshop, Boulder/CO