1. Baseline findings in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study.;Zadnik;Invest Ophthalmol Vis Sci,1998
2. Clinical management of keratoconus: a multicenter analysis.;Lass;Ophthalmology,1990
3. Contact Lenses.;Phillips,1997
4. Contact Lens Practice.;Mandell,1988
5. Cornea, 2nd ed.;Feder,2005