1. ADAM, C. (1911). Z. Augenheilk., 25, 330.
2. BERRISFORD, P. D. (1916). Roy. Lond. Ophthal. Hosp. Rep., 20, 296.
3. COLLINS, E. T. (1892). Ibid., 13, 361.
4. COLLINS, E. T. (1895). Ibid., 14, 52.
5. CUMINGS, J. N., and SORSBY, A. (1944). British journal of Ophthalmology, 28, 333.