1. Ho-Nyun Lee et al., Proc. SID'07, p 1826, 2007.
2. Takashi Hirao t al., Proc. SID'06, p 18, 2006.
3. M. Ito, et al. Proc. IDW'06, p 585, 2006.
4. Sang-Hee Ko Park et al., Proc. SID'06, p 25, 2006.
5. Jang Yeon Kwon et al., Digest of IMID'07, p. 141, 2007.