1. N. Berthet, ?Three Nb-Ti superconducting magnets differing in conception and operating temperature,? Proceedings of the Fourth International Cryogenic Engineering Conference, Eindhoven (1972), pp. 209?213.
2. M. N. Biltcliffe, P. E. Hanley, I. B. McKinnon, and P. Roubeau, ?Operation of superconducting magnets at temperatures below 4.2 K,? Cryogenics, No. 2, 44?47 (1972).
3. H. Kobayashi, K. Ecomoto, and K. Iosukochi, ?Construction and operation of a cryostat for pressurized superfluid helium,? Cryog. Eng.,16, No. 1, 21?28 (1981).
4. G. Cloudet, A. Lacoze, P. Roubeau, and I. Verdier, ?Design and operation of refrigerator system using superfluid helium,? Proceedings of the Fifth Cryogenic Engineering Conference, Kyoto (1974), pp. 265?267.