参考文献:
Berthel, Steven Joseph Kester, Robert Francis Murphy, Douglas Eric Prins, Thomas Jay Ruebsam, Frank Sarabu, Ramakanth Tran, Chinh Viet Vourloumis, Dionisios Patent: US2008/21032 A1, 2008 Location in patent: Page/Page column 45 US 20080021032 A1