Variscite from Lawrence County, South Dakota, USA
USA | |
| Loomis, T. (2011), "News from the Black Hills, South Dakota", Mineral News, in press |
| Smith, Arthur E., Fritzsch, Eric (2000) SOUTH DAKOTA. Rocks & Minerals, 75 (3) 156-169 doi:10.1080/00357520009605635 |