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USA | |
| Samuel S. Gordon (1922) Mineralogy of Pennsylvania. Mineralogy of Pennsylvania-1922 Samuel S. Gordon, pg. 234 pg. 234 |
| Mineralogy of Pennsylvania-1922 Samuel S. Gordon, pg. 221-222 |
| The Mineral Collector, Vol. 1, No. 12, pg. 190, (February 1895). |
| Gordon, 1922. Mineralogy of Pennsylvania |
| Gordon, Mineralogy of Pennsyvania, 1922 - p. 224 |
| Ref.: Gordon, S.G. (1922) "The Mineralogy of Pennsylvania," Special Publication No. 1, The Academy of Natural Sciences of Philadelphia: p. 125. |
| Mineralogy of Pennsylvania-1922 Samuel S. Gordon, pg. 229 |
| Benge and Wherry, XIII, 1. c. |
| Samuel G. Gordon (1922) "Mineralogy of Pennsylvania" p. 225. |
| Samuel G. Gordon (1922) "Mineralogy of Pennsylvania" p. 225. |
| Gordon, 1922. The Mineralogy of Pennsylvania |