Hamilton, C.W.; Reichard, S.H. (1992). "Current practice in the use of subspecies, variety, and forma in the classification of wild plants". Taxon. 41 (3): 485–498. doi:10.2307/1222819. JSTOR1222819.
Hamilton, C.W.; Reichard, S.H. (1992). "Current practice in the use of subspecies, variety, and forma in the classification of wild plants". Taxon. 41 (3): 485–498. doi:10.2307/1222819. JSTOR1222819.