参考文献:
Teegarden, Bradley Xiong, Yifeng Strah-Pleynet, Sonja Jayakumar, Honnappa Dosa, Peter I. Feichtinger, Konrad Casper, Martin Lehmann, Juerg Jones, Robert M. Unett, David J. Karoline Choi, Jin Sun Patent: US27/27994 A, 27 Location in patent: Page/Page column 56 US 2727994 A