Fossil wood and lignite of the Potomac formation Knowlton, Frank Hall 1860-1926 creator author. Geological Survey (U.S.) issuing body. text bibliography dcu 1889 monographic eng remote 1 online resource (72 pages, VII pages of plates) : illustrations. by Frank Hall Knowlton. Title from title screen (viewed June 23, 2014). Includes bibliographical references and index. n-us--- Lignite Paleobotany Cretaceous Paleobotany United States Cretaceous Geologic Period Lignite Paleobotany United States From 65 to 140 million years ago fast I 19.3:56 I 19.3:56 Fossil wood and lignite of the Potomac formation Knowlton, Frank Hall (OCoLC)4891922 Bulletin of the United States Geological Survey ; no. 56 https://purl.fdlp.gov/GPO/gpo57645 COP 140626 20211120173049.0 in00003536013 eng