1. C. S. Pang, C. M. Falco, R. J. Kampwirth, I. K. Schuler, J.J. Hudak, and T. A. Anastasio in “Advances In Cryogenic Engineering, Vol. 25”, Plenum Press, New York (1980), p. 244.
2. C. W. Smith, in “Science and Technology of Surface Coating”, Academic Press, London (1974), pp. 262–269.
3. J. J. Hudak, “Precision Linear Tuning Circuit”, U.S. Patent No. 4,375,626, March 1, 1983.
4. A. von Hippel and W. B. Westphal, Technical Report 145, M.I.T. Laboratory for Insulation Research, Dec. 1959.