Johnson et al., 1959. USDA, Farmers' Bulletin, N°2129 Document reference Johnson, H. W. ; Carter, J. L. ; Hartwig, E. E., 1959. Growing soybeans. USDA, Farmers' Bulletin, N°2129Web http://books.google.fr/books?id=l1J98v909XwCCitation key Johnson et al., 1959Datasheets Soybean forage
