1. Brit;COLE, R.B.W.;med. J,1959
2. DOWNING, A. H. (1945) Ibid., 33, I37 FLOM, M. C., and NEUMAIER, R. W. (1966) Pub. Hlth Rep. (Wash.), 8I, 329
3. GANSNER, j. (1968) Ophthalmologica (Basel), 155, 234
4. Amer;HELVESTON, E.M.;J. Ophthal; Rank Correlation Methods,1965