1. F. Braun, “Ueber die Stromleitung durch Schwefelmetalle (“On Current Flow through Metallic Sulfides”), Annalen der Physik und Chemie
153, 556, (1874).
2. Many references such as C. Kittel, Introduction to Solid State Physics, 5th Edition, Wiley (1976) mistakenly state that the IV–VI compounds PbS, PbSe, PbTe are indirect gap semiconductors.
3. U. Schiessl, J. John, P. J. McCann, “Lead-Chalcogenide-based Mid-Infrared Diode Lasers”, Long-Wavelength Infrared Semiconductor Lasers, p. 145, H.K. Choi (Editor), Wiley, New York (2004).
4. C. B. Roller, K. Namjou, J. Jeffers, W. Potter, P. J. McCann, and J. Grego, “Simultaneous NO and CO2 Measurements in Human Breath Using a Single IV–VI Mid-Infrared Laser”, Optics Letters
27, 107 (2002).
5. C. B. Roller, K. Namjou, J. Jeffers, M. Camp, P. J. McCann, and J. Grego, “Nitric Oxide Breath Testing Using Tunable Diode Laser Absorption Spectroscopy: Application in Respiratory Inflammation Monitoring”, Applied Optics
41, 6018 (2002).