参考文献:
Carruthers, Nicholas I. Chai, Wenying Dax, Scott L. Jablonowski, Jill A. Li, Xiaobing Lovenberg, Timothy W. Murray, William V. Rudolph, Dale A. Seierstad, Mark Youngman, Mark A. Patent: US5/7534 A, 5 Location in patent: Page/Page column US 57534 A