1. Logarithmic Sector vs. Photoelectric Densitometer in Measuring Intensity Ratios
2. Harrison Lord and Loofbourow, Practical Spectroscopy, Prentice Hall, Inc., New York, 1948, pp. 335–6
3. Twyman F., Metal Spectroscopy, Chas. Griffin & Co., Ltd., London, 1951, pp. 269–73
4. A Step-Sector for the Astigmatic Spectrograph
5. Mees C. E. K., Theory of the Photographic Process, The MacMillan Co., New York, p. 236