1. Quasi-Zenith Satellite System Interface Specification, Centimeter Level Augmentation Service IS-QZSS-L6-00 http://qzss.go.jp/en/technical/ps-is-qzss/ps-is-qzss.html
2. Quasi-Zenith Satellite System Interface Specification, Satellite Positioning, Navigation and Timing Service http://qzss.go.jp/en/technical/ps-is-qzss/ps-is-qzss.html
3. BeiDou Navigation Satellite System, Signal in Space Interface Control Document, Open Service Signal http://www.beidou.gov.cn/attach/2016/11/07/21212.pdf
4. USA/European Community Agreement on the Promotion, Provision and Use of Galileo and GPS Satellite-Based Navigation Systems and Related Applications 2004