1. Average radar cross section (sq. m.) as of 1 July 1977, report;Aerospace Defense Command,1977
2. NASA Spec. Publ. SP-345;Alfvén,1976
3. NASA Tech. Note TND-8108;Bess,1975
4. Bowman, N. J., , The Handbook of Rockets and Guided Missiles, Perastadion Press, Newtown Square, Pa., 1963,
5. Predicting the probability that earth-orbiting spacecraft will collide with man-made objects in space;Brooks,1975