Hoover, B. K., (2013). HortTechnology 23(1), 44-50. American Society for Horticultural Science, Alexandria, USA. English language
Jones, G. E., Cregg, B. M., (2006). HortScience 41(1), 143-148. American Society for Horticultural Science, Alexandria, USA. English language
Robinson, J. F., Thor, E., (1969). Forest Science 15(3), 238-45. English language
Fernald, M. L., (1950). A Handbook of the Flowering Plants and Ferns of the Central and Northeastern United States and Adjacent Canada.(Edn 8) American Book Company, New York, USA. English language