E.-C. Kang, N.-Y. Hong, C.-H. Jang, K.-W. Song, and J.-O. Lee, “Phase Transition Behavior of Poly(N-isopropylacrylamide-co-N,Ndimethylaminopropylacrylamide) Hydrogels”, Eurasian Chem.-Technol. J., vol. 4, no. 2, pp. 113–117, Mar. 2002.