| 其他書名 | Field Trip Guidebook to Silurian Exposures in Jones and Linn Counties |
| 出版 | Iowa Department of Natural Resources, Energy and Geological Resources Division, Geological Survey Bureau, 1992 |
| URL | http://books.google.com.hk/books?id=tO2vT2R3TgwC&hl=&source=gbs_api |