A. Brooks, P. MacCready, P. Lissaman, and W. Morgan. 21st Joint Propulsion Conference, page 59--67. Monterey, US-CA, American Institute of Aeronautics and Astronautics, (July 1985)
S. Pagar, S. Baviskar, V. Chalwadi, and P. Kumavat. International Journal on Recent and Innovation Trends in Computing and Communication, 3 (1):
05--10(January 2015)