1. Baylis, J.A., Electrical Times, Issue 4232, 9, (1973).
2. Graeme-Barber, C. Maddock, B.J., Popley, R.A. and Smedley, P.N. Cryogenics, 12, 317, (1972).
3. Appleton, A.D. and Bartram, T.C., Third Ship Control Systems Symposium, Ministry of Defense, Foxhill, Bath, Somerset, (1972).
4. Appleton, A.D. and Anderson, A.F., Proc. 1972 Applied Superconductivity Conference, Annapolis, p. 136, IEE Pubi. 72CH0682–5- TABSC (1972).
5. Wilson, M.N., RHEL/M/A26.