参考文献:
Arienti, Kristen L. Breitenbucher, J. Guy Buzard, Daniel J. Edwards, James P. Hack, Michael D. Khatuya, Haripada Kindrachuk, David E. Lee, Alice Venable, Jennifer D. Patent: US005/70550 A, 005 Location in patent: Page/Page column 34 US 0050070550 A