1. BuRIAN, H. M. (1941). Arch. Ophthal. (Chicago), 26, 626.
2. CASHELL, G. T. W. (1950). Brit. orthoptic J., 7, 45.
3. Text-book of Ophthalmology;DUKE-ELDER, S.,1949
4. Kimpton, London. GrrroEs-DAvIEs, R. (1952). Brit. orthoptic J., 9, 113.
5. GRAHAM, P. A. and NAYLOR, E. J. (1957). Brit. J. Ophthal., 41, 425.