|
USA | |
| Ransom, Jay Ellis (1974) Gems and Minerals of America - A Guide to Rock Collecting. Harper & Row. |
| Ladd, Harry S. (1944) Manganese Deposits Of The Sweet Springs District West Virginia And Virginia : USGS Bulletion 940-G |
| Ladd, Harry Stephen (1944), Manganese Deposits of the Sweet Springs District West Virginia and Virginia, USGS Bulletin 940-G. |
| Ladd, Harry S. (1944) Manganese Deposits Of The Sweet Springs District West Virginia And Virginia : USGS Bulletion 940-G |
| Ladd, Harry Stephen (1944), Manganese Deposits of the Sweet Springs District West Virginia and Virginia, USGS Bulletin 940-G. |
| Ladd, Harry S. (1944) Manganese Deposits Of The Sweet Springs District West Virginia And Virginia : USGS Bulletion 940-G |
| Ransom, Jay Ellis (1974) Gems and Minerals of America - A Guide to Rock Collecting. Harper & Row. |