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2. Wright, “Researches in Normal and Defective Colour Vision” (London: H. Kimpton, 1946).
3. Thomson and Trezona, J. Physiol. (in the press).
4. Lythgoe, Brit. J. Ophthal., 24, 21 (1940).
5. Granit, “Sensory Mechanisms of the Retina” (Oxford University Press, 1947).