1. V. Lounasmaa, “Experimental Principles and Methods Below 1 K,” Academic Press, New York (1974)
2. S. Castles, private communication (1986)
3. H. W. Jackson, Can 3He-4He dilution refrigerators operate aboard spacecraft?, Cryogenics 22, 59 (1982)
4. H. W. Jackson, unpublished
5. Emerson & Cuming, Inc., Gardena, CA