1. Solution of the Problem of Artificial Satellite Theory without Drag;Brouwer;Astronomical Journal,1959
2. An Economical Semi-Analytical Orbit Theory for Micro-Computer Applications;Gordon;AIAA Paper 86-0085 (1986) & NASA Technical Paper 2811,1988
3. Autonomous Spacecraft Navigation for Earth Ground Track Repeat Orbiti Us-ing GPS;Guinn,1980
4. Models for propagation of NORAD element sets;Hoots,1980
5. 2nd ed. by Kelso T. S., December (1988).