M. J. Roncada, D. Wilson, A. Lui Netto, O. Berretta Netto, and A. C. Kalil, “ Investigation on prevalence of xerophthalmia among patients of Brazilian ophthalmologists ”, Rev. saúde pública, vol. 12, no. 2, pp. 151–156, Jun. 1978, doi: 10.1590/S0034-89101978000200007.