1. ASHTON, N., and CHOYCE, D. P. (1959). Brit. J. Ophthal., 43, 577.
2. KIEWE, P. L., and HART, F. DUDLEY (1951). Trans. ophthal. Soc. U.K., 71, 309.
3. MANSCHOT, W. A. (1959). See BINKHORST, C. D. (1959). Klin. Mbl. Augenheilk., 134, 536 (Fig. 6 on p. 539).