United States. Bureau of Public Roads. (1930). Subgrade soil exhibit of Bureau of Public Roads, U.S. Department of Agriculture, 6th Congress of Permanent International Association of Road Congresses. U.S. GPO.
Chicago Style (17th ed.) CitationUnited States. Bureau of Public Roads. Subgrade Soil Exhibit of Bureau of Public Roads, U.S. Department of Agriculture, 6th Congress of Permanent International Association of Road Congresses. Washington: U.S. GPO, 1930.
MLA (9th ed.) CitationUnited States. Bureau of Public Roads. Subgrade Soil Exhibit of Bureau of Public Roads, U.S. Department of Agriculture, 6th Congress of Permanent International Association of Road Congresses. U.S. GPO, 1930.
Warning: These citations may not always be 100% accurate.