Gilman, Arthur V., and Arthur Haines. “Rediscovery of Crataegus Pisifera (Rosaceae: Maleae)”. Journal of the Botanical Research Institute of Texas 16, no. 2 (November 29, 2022): 357–372. Accessed April 26, 2024. https://journals.brit.org/jbrit/article/view/1255.