1. W.J. Buehler and R.C. Wiley, U.S. patent 3,174, 851 (1965).
2. (Paper presented at the 8th Int;Heisterkamp,1969
3. W.J. Buehler F.E. Wang (Paper presented at the Ninth Navy Science Symposium 1966 Washington D.C.
4. G.B. Kauffman and I. Mayo, Invention and Technology, Fall (1993), pp. 18–23.