1. V. K. Zworykin et al.,Electron Optics and the Electron Microscope(John Wiley & Sons, Inc., New York, 1945) p. 328 ff.
2. John Strong,Procedures in Experimental Physics(Prentice-Hall, Inc., New York, 1945). Chap. 4.
3. I. M. Kolthoff and E. B. Sandell,Quantitative Inorganic Analysis(The Macmillan Company, New York, 1936), p. 306.
4. L. Schulz of the Institute for the Study of Metals has kindly pointed out that porosity may account for 10 percent of the volume in evaporated foils. The only precaution taken against this was to perform the evaporation very slowly, i.e., for periods of from 5 to 10 minutes.