1. Crank, J. 1956.The Mathematics of Diffusion, 10Oxford University Press.
2. Drummond, I. W. 1968. University of Cambridge. Ph.D. dissertation
3. Drummond, I. W. and Long, J. V. P. 1969. Proceedings of the First International Conference on Ion Sources. 1969. pp.459Saclay: I.N.S.T.N.
4. Garner, W. E. 1955.Chemistry of the Solid State, 30Butterworths.