1. Oxford Instruments LTD, Osney Mead, Oxford OX2 ODX, England
2. S.H.E. corporation, 4174 Sorrento Valley Blvd.,San Diego,U.S.A.
3. An introductional description of this cooling technique as well as the technique of dilution refrigeration can be found in: O.V. Lounasmaa, Experimental principles and methods below 1K. Academic Press Inc. (London) 1974 and
4. O.V. Lounasmaa. J. Phys. E 12 (1979) 668 and
5. D.S. Betts, Refrigeration and thermometry below 1K. Sussex University Press (1976)