1. Ultrastructural studies on graptolites Author/Creator: Urbanek, Adam Publication/Creation: Washington : Smithsonian Institution Press; [for sale by the Supt. of Docs., U.S. Govt. Print. Off.], 1974-75. Resource Type: Book Access & Availability: Loading
2. Upper Cambrian-Lower Ordovician Notch Peak Formation in western Utah Author/Creator: Hintze, Lehi F. Publication/Creation: Denver, CO : For sale by the Books and Open-File Reports Section, U.S. Geological Survey Resource Type: Book Access & Availability: Loading
3. Upper Ordovician ecology of the central Appalachians Author/Creator: Bretsky, Peter William, 1938- Publication/Creation: New Haven : Peabody Museum of Natural History, Yale University, 1970 Resource Type: Book Access & Availability: Loading