by L. G. Berry and R. M. Thompson. by A. G. Martin and F. W. Stephenson. W. Feit and J. G. Thompson. by H. J. Emeleus and J. S. Anderson. by K. J. Binns and P. J. Lawrenson. by I. F. Henderson and W. D. Henderson. by A. Yariv and J. E. Pearson. by J.R. Lucas and P.E. Hodgson. by W. G. McLean and E. W. Nelson. by David Benzie and A. T. Phillipson.