1. Ammon. Quoted by Manz, Graefe Saemisch Handbuch, 1st ed., 1876, p. 117.
2. Liebreich, R. 1863. Atlas of Ophthalmosc., pl. vii. fig. 3, 2nd ed., pl. xii, fig. 3.
3. Del Monte, M. 1872. Manuale practico di Oftalmiatria. 1872. Nagel's Jahresbericht, p. 244, 1872
4. Schöler. 1882. Berlin med. Gesellsch. Quoted by Paget, q. r.