Gunn, C. R. 1., Wiersema, J. H. 1., Ritchie, C. A., & Kirkbride, J. H. 1. (1992). Families and genera of spermatophytes recognized by the Agricultural Research Service. Beltsville, Maryland: United States, Department of Agriculture, Agricultural Research Service.
Chicago Style CitationGunn, Charles R. 1927-, John Harry 1950- Wiersema, Carole A. Ritchie, and Joseph Harold 1943- Kirkbride. Families and Genera of Spermatophytes Recognized By the Agricultural Research Service. Beltsville, Maryland: United States, Department of Agriculture, Agricultural Research Service, 1992.
MLA CitationGunn, Charles R. 1927-, John Harry 1950- Wiersema, Carole A. Ritchie, and Joseph Harold 1943- Kirkbride. Families and Genera of Spermatophytes Recognized By the Agricultural Research Service. Beltsville, Maryland: United States, Department of Agriculture, Agricultural Research Service, 1992.