Siltstone from South Dakota, USA
USA | |
| Richardson G. B., (1903), The Upper Red Beds of the Black Hills, The Journal of Geology, Vol. 11, No. 4 (May – June). |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| Vickers, R. C. (1954). Occurrences of radioactive minerals in the Bald Mountain gold-mining area, northern Black Hills, South Dakota: US Geol. Survey Circ, 351(8). |