1. Misra P, Enge P. Global positioning system: signals, measurements, and performance. Lincoln, MA: Ganga-Jamuna Press; 2004.
2. Kaplan ED, Hegarty CJ. Understanding GPS: principles and applications. Artech House; 2005.
3. http://www.gps.gov/systems/gps/modernization/ .
4. http://www.nis-glonass.ru/en/glonass/ .
5. http://www.esa.int/Our_Activities/Navigation .