Digital mineral resource maps of phosphate and natural aggregate for the Pacific Northwest : a contribution to the Interior Columbia River Basin Ecosystem Management Project
Includes bibliographical references (pages 20-23).
Also issued in paper format.
Mode of access: Internet from the USGS web site. Address as of 6/9/08: http://pubs.usgs.gov/of/1995/of95-681/of95-681.pdf; current access available via PURL.