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USA | |
| Frondel, Clifford (1956) Mineral composition of gummite. American Mineralogist, 41 (7-8) 539-568 |
| Whitmore, Robert W., Lawrence, Robert C. Jr. (2004) The Pegmatite Mines known as Palermo. Friends of Palermo Mines, North Groton, NH. |
| Januzzi, Ron E., Seaman, David M. (1976) Mineral Localities of Connecticut and Southeastern New York State and Pegmatite Minerals of the World. The Mineralogical Press, Danbury, Connecticut, USA. |
Ruggles Mine, Grafton, Grafton County, New Hampshire, USA