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2. , and HUNTER, W. S. (1971) Ibid., 6, i83
3. ALEXANDER, R. L., and SHEA, M. (1964) Arch. Ophthal. (Chicago), 72, 498
4. ARCHILA, E. A. (1970) Rev. Soc. colomb. Oftal., I, 45
5. Statistical Methods in Medical Research;ARMITAGE, P.,1971