03- Négrel A, Maul E, Pokharel G, Zhao J, Ellwein L. Refractive error study in children: sampling and measurement methods for a multi-country survey. Am J Ophthalmol 2000;129:421-6.

03- Négrel A, Maul E, Pokharel G, Zhao J, Ellwein L. Refractive error study in children: sampling and measurement methods for a multi-country survey. Am J Ophthalmol 2000;129:421-6.