1. Fuchs, A.-Amer. Ji. of Ophthal., Vol. VII, No. 6, 1924 (compare the diagrams).
2. Stood.-Klin. Monatsbl. f. Augenheilk., p. 288, 1884.
3. Monografie des Sehnervenkopfes in mensclichen Auges;Szily, Adolf,1901
4. Ronne -Arch. f. Oihthal., Vol. CV, p. 465.
5. Leber.-Arch. f. OJhthal., Vol. XXV 1, Pt. ii, 1880.