参考文献:
Curtis, Michael Duclos, Brian A. Ewin, Richard A. Johnson, Paul D. Johnson, Timothy Allen Vairagoundar, Rajendran Billen, Denis Goodwin, Richard M. Haber-Stuk, Andrea K. Kyne, Graham M. Sheehan, Susan M. K. Patent: US3/375 A, 3 Location in patent: Paragraph 397