1. Global Positioning System Standard Positioning Service Signal Specification GPS Civil Performance Standard U.S. Department of Defense November 5 1993. Can be found at:https://www.gps.gov/technical/ps/1993‐SPS‐signal‐specification.pdf
2. A History of Satellite Navigation
3. BeiDou Navigation Satellite System Open Service Performance Standard (Version 1.0) China Satellite Navigation Office December2013.
4. European GNSS (Galileo) Initial Service—Open Service—Service Definition Document issue 1.0 European Union December2016(OS SDD V1.0). Can be found at:https://www.gsc‐europa.eu/system/files/galileo_documents/Galileo‐OS‐SDD.pdf