1. BORSCHKE, A. (1904).--Wien. Med. Wschr., Suppl. der Militairarzt. (1904).-Arch. f. Augenheilk., Vol. LII, p. 161.
2. -Arch.f. Augenheilk., Vol. LIV, p. 376.
3. -Arch. f. Augenheilk., Vol. LVIII, p. 292.
4. Dictionary of Applied Physics, Vol;IV
5. In v. Helmholtz Handbuch d. physiol. Optik;GULLSTRAND, A.,1909