1. Alexander K.R., et al., 1992, Grating, vernier, and letter acuity in retinitis pigmentosa Invest Ophthalmol Vis Sci. 33:3400–3406.
2. Elliott D.B., K. Sanderson, and A. Conkey, 1990, The reliability of the Pelli-Robson contrast sensitivity chart Ophthalmic Physiol Opt. 10:21–24.
3. Farber M.D., G.A Fishman, and R.A. Weiss, 1985, Autosomal dominantly inherited retinitis pigmentosa. Visual acuity loss by subtype. Arch Ophthalmol. 103:524–528.
4. Hirohido H., Hiroyuki Iijima., Takashi Gohdo., Masahito Imai.,and Shigeo Tsukahara., 1999, Progression of defect in the central 10-degree visual field of patients with retinitis pigmentosa and choroideremia. Am J Ophthalmology 127:436–442.
5. Likert R.A., 1932, Technique for the measurment of attitude. Arch Psycology 140:1–55.