1. Abraham, D. (2015). The elements of power: Gadgets, guns, and the struggle for a sustainable future in the rare metal age. New Haven: Yale University Press.
2. Bleiwas, D. I., Papp, J. F., & Yager, T. R. (2015). Shift in global tantalum mine production, 2000–2014. U.S. Geological Survey Fact Sheet 2015–3079. doi:
10.3133/fs20153079
.
3. Brininstool, M. (2014). Copper. In Mineral commodity summaries 2014 (pp. 48–49). Washington: U.S. Geological Survey.
https://minerals.usgs.gov/minerals/pubs/mcs/2014/mcs2014.pdf
.
4. Brininstool, M. (2017). Copper. In Mineral commodity summaries 2017 (pp. 54–55). doi:
10.3133/70180197
.
5. Chasan, E. (2015). “Conflict minerals” prove hard to trace. The Wall Street Journal. 4 August (p. B4).