^Sumi, H.; Hamada, H.; Tsushima, H.; Mihara, H.; Muraki, H. (1987). “A novel fibrinolytic enzyme (nattokinase) in the vegetable cheese Natto; a typical and popular soybean food in the Japanese diet”. Experientia43 (10): 1110–1111. doi:10.1007/BF01956052. PMID3478223.
^Chang YY, Liu JS, Lai SL, Wu HS, Lan MY (2008). “Cerebellar hemorrhage provoked by combined use of nattokinase and aspirin in a patient with cerebral microbleeds”. Intern. Med.47 (5): 467–9. PMID18310985.
^Cho L (April 2007). “Ask the doctor: I have read good news about nattokinaze and would like to use it to keep my blood thin. Is it a good substitute for aspirin?”. Heart Advis10 (4): 8. PMID17500089. "Not very much is known about nattokinaze... there is not enough information from human studies to know for sure what it can do or to recommend it for people with cardiovascular disease. Aspirin should be your first choice."