Willard, B. (1939). Guide to the geology of the upper Schuylkill Valley: By Bradford Willard. Department of Internal Affairs, Topographic and Geologic Survey.
Chicago Style (17th ed.) CitationWillard, Bradford. Guide to the Geology of the Upper Schuylkill Valley: By Bradford Willard. Harrisburg, Pa.: Department of Internal Affairs, Topographic and Geologic Survey, 1939.
MLA (9th ed.) CitationWillard, Bradford. Guide to the Geology of the Upper Schuylkill Valley: By Bradford Willard. Department of Internal Affairs, Topographic and Geologic Survey, 1939.
Warning: These citations may not always be 100% accurate.