1. B. Petkof, “Gallium,” Mineral Facts and Problems, 1985 Edition, Bureau of Mines B 675, 1985, pp. 291–296.
2. P.A. Plunkert, “Germanium,” Mineral Facts and Problems, 1985 Edition, Bureau of Mines B 675, 1986, pp. 317–322.
3. H. Brody, “Ultrafast Chips at the Gate,” High Technology, V. 6, No. 3, 1986, pp. 28–35.
4. Mining Annual Review, “Gallium and Germanium,” 1986, pp. 94–95.
5. J.G. Parker, “Occurrence and Recovery of Certain Minor Metals in the Processing of Lead and Zinc,” Bureau of Mines IC 8790, 1979.