Hussain, Ali Shabbir, et al. “ORAL SILDENAFIL USE IN NEONATES WITH PERSISTENT PULMONARY HYPERTENSION OF NEWBORN”. Journal of Ayub Medical College Abbottabad, vol. 29, no. 4, Oct. 2017, pp. 677-80, https://jamc.ayubmed.edu.pk/index.php/jamc/article/view/2621.