Ullah, F., M. A. Shah, M. N. Khan, F. Rahim, and M. Bashir. “Congenital Nasolacrimal Duct Obstruction at Agency Headquarter Hospital Batkhela NWFP”. Journal of Postgraduate Medical Institute, vol. 18, no. 3, Oct. 2011, https://www.jpmi.org.pk/index.php/jpmi/article/view/921.