by E. A. Guggenheim and R. H. Stokes. by R. A. Robinson and R. H. Stokes. by B. W. Preece and J. D. Davies. by R.A. Robinson and R.H. Stokes. by A. E. Vines and N. Rees. by A. E. Gillam and E. S. Stern. by A. H. Sully and E. A. Brandes. by R. B. Heslop and K. Jones. by I. I. Berenblut and Anne B. Downes.