United States. Department of Agriculture. Office of the Secretary & McKee, R. (1923). History and seed production of purple vetch. [publisher not identified].
Chicago Style (17th ed.) CitationUnited States. Department of Agriculture. Office of the Secretary and Roland McKee. History and Seed Production of Purple Vetch. Washington: [publisher not identified], 1923.
MLA (9th ed.) CitationUnited States. Department of Agriculture. Office of the Secretary and Roland McKee. History and Seed Production of Purple Vetch. [publisher not identified], 1923.
Warning: These citations may not always be 100% accurate.