1. Fischer, F. (1931). Z. Augenheilk., 75, 343.
2. Fischer, F. (1935). Ibid., 85, 88.
3. Hagedoom, A. (1937). Amer. J. Ophthal., 20, 690.
4. Rand, C. W., and Andler, M. (1950). Arch. Neurol. Psychiat.
5. Walsh, F. B. (1947). Clinical Neuro-Ophthalmology, p. 1161. Williams and Wilkins, Baltimore.