参考文献:
Andreini, Matteo Banner, David Guba, Wolfgang Hilpert, Hans Mauser, Harald Mayweg, Alexander V. Narquizian, Robert Power, Eoin Roger-Evans, Mark Travagli, Massimiliano Valacchi, Michela Woltering, Thomas Wostl, Wolfgang Patent: US2/4622 A, 2 Location in patent: Page/Page column 3-32 US 24622 A