D. Radhy, N. “Naproxen Sodium Release from Poly(acrylic Acid-Co- N-Vinyl-2-Pyrrolidone) Hydrogels”. Al-Qadisiyah Journal of Pure Science, Vol. 21, no. 1, July 2018, pp. 64 -76, https://journalsc.qu.edu.iq/index.php/JOPS/article/view/41.