Ahn, Sung Oh; Park, Chan Hee; Im, Jun Hwan; Lee, Soon Ok; Lee, Kyoung June; Cho, Seong Wook; Ko, Kwang Seok; Han, Sun Young; Lee, Won Il Patent: US2011/28467 A1, 2011 ; Location in patent: Page/Page column 15 ; US 20110028467 A1