1. 3) T. Asada et al., Nature 143, 797 (1939).
2. 6) V. Zworykin et al., “Electron Optics and the Electron Microscope,” John Wiley and Sons Inc., New York (1945).
3. 7) H. Ewalt und H. Hintenberger, “Methoden und Anwendung der Massenspektroskopie,” Verlag Chemie, GMBH, Weinheim/Bergstrasse (1953).
4. 8) Nat. Bur. Stand., Circ. 522; Mass Spectroscopy in Physics Research (1953).
5. 20) R. R. Gordon, in “Advances in Mass Spectrometry,” Vol. 3, ed. by W. L. Mead (1966), p. xiii.