I. Hong Ooi, S. Hui Ng, Y. Kie Chong, and S. Kiat Wong, “Swelling Properties of Poly(N-isopropylacrylamide)/Calcium Alginate Interpenetrating Polymer Network Hydrogel containing Zirconia”, ajc, vol. 27, no. 9, pp. 3489–3493, May 2015.