Ismail, Natheer Nori. 2017. “Experimental Study on Ion Exchange Rate of Calcium Hardness in Water Softening Process Using Strong Acid Resin DOWEX HCR S S”. Nahrain University College of Engineering Journal 19 (1): 107-14. https://oldjournal.eng.nahrainuniv.edu.iq/index.php/main/article/view/50.