1. Mars Pathfinder Homepage http:// nssdc.gsfc.nasa.gov/planetary/mesur.html.
2. Mars Spirit and Opportunity Rovers Homepage, http://marsrovers.jpl.nasa.gov/home/
3. Optimal Path Planning Based on Visibility
4. Optimal motion planning for mobile observers based on maximum visibility, Dynamics of Continuous, Discrete and Impulsive Systems, 11 (2004), 313-338.