Aaronson, K. et al. (2003). Interaction study between Digoxin and a preparation of  Hawthorn (Crataegus oxyacantha. The Journal of Clinical Pharmacology, 43, 637-642.

 Beresford-Kroeger, D. (2006). Arboretum America: a philosophy of the forest. USA: The Universiy of Michigan Press.

 Bowman, M. (2006). The holy thorn ceremony: revival, rivalry and civil religion. Folklore, 117(2), 123-140.

 Gilman, E.F., & Watson, D.G. (1993). Crataegus phaenopyrum Washington Hawthorn. U.S. Department of Agriculture, Forest Service Fact Sheet.

 Grimassi, R. (2003). Encyclopedia of wicca and witchcraft. St. Paul Minnesota: Llewellyn Publications.

 Missouri Botanical Garden. Crataegus phaenopyrum. Retrieved from http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/plant-finder/plant-details/kc/a861/crataegus-phaenopyrum.aspx.

 Studier, E. et al. (1987). Nutritional budgets in free flying birds: Cedar Waxwings feeding on Washington Hawthorn fruit. Comparitive Biochemistry and Physiology Part A: Physiology, 89(3), 471-474.

Tassell, M. et al. (2010). Hawthorn in the treatment of cardiovascular disease. Pharmacognosy Review, 4(7), 32-41.