参考文献:
Brewster, William Kirkland Klittich, Carla Jean Rasmussen Balko, Terry William Breaux, Nneka Tuere Erickson, William Randal Hunter, James Edward Lowe, Christian Thomas Ricks, Michael John Siddall, Thomas Lyman Yerkes, Carla Nanette Zhu, Yuanming Patent: US6/8937 A1, 6 Location in patent: Page/Page column 35