1. California Institute of Technology, 1999. Automated GIPSY Analyses, http://milhouse.jpInasa.gov/ag/.
2. Commonwealth of Australia, 2000. AUSLIG Online GPS Processing Service, http://www.auslig.gov.au/cgi-bin/gps.cgi.
3. GPS Solutions Inc. 2000. High Accuracy GPS Data Analysis and Consulting, http://www.gps-solutions.com/.
4. GPS Solutions Inc. 2000. GPS Data Analysis, http://www.gps-solutions.com/cgi-bin/gps.cgi.