1. W. E. Gifford and R. C. Longsworth, in: Advances in Cryogenic Engineering, Vol. 11, Springer Science+Business Media New York (1966), p. 171.
2. R. A. Ackermann, “Investigation of Gifford-McMahon Cycle and Pulse Tube Cryogenic Refrigerators,” Research and Development Tech. Rept. ECOM-3245, U. S. Army Electronics Command, Ft. Monmouth, New Jersey, March 1970.
3. R. C. Longsworth, Ph.D. Dissertation, Syracuse University, Syracuse, New York (1966).
4. R. A. Lechner, “Investigation of Regenerators and Pulse Tube Cryogenic Coolers,” Research and Development Tech. Rept., ECOM-3409, U.S. Army Electronics Command, Ft. Monmouth, New Jersey, May 1971.