Hyun Sam Ryu, Seong-Jae Mun, Tae Seop Lim, Hong-Chan Kim, Kwang-Seon Shin, and Seong-Hyeon Hong, “Microstructure Evolution During Plasma Electrolytic Oxidation and Its Effects on the Electrochemical Properties of AZ91D Mg Alloy”, Journal of The Electrochemical Society, 158 (9) C266-C273 (2011)