1. http://www.silicondesigns.com/tech.html .
2. Cloudcap technology. http://www.cloudcaptech.com .
3. Micropilot. http://www.micropilot.com/ .
4. Procerus technologies. http://procerusuav.com/ .
5. Brian D.O. Anderson and John B. Moore. Optimal Control: Linear Quadratic Methods. Prentice Hall, Englewood Cliffs, New Jersey, 1990.