Burton GJ, Watson AL, Hempstock J, Skepper JN, Jauniaux E (xuño de 2002). "Uterine glands provide histiotrophic nutrition for the human fetus during the first trimester of pregnancy". J. Clin. Endocrinol. Metab.87 (6): 2954–9. PMID12050279. doi:10.1210/jcem.87.6.8563.
Burton GJ, Watson AL, Hempstock J, Skepper JN, Jauniaux E (xuño de 2002). "Uterine glands provide histiotrophic nutrition for the human fetus during the first trimester of pregnancy". J. Clin. Endocrinol. Metab.87 (6): 2954–9. PMID12050279. doi:10.1210/jcem.87.6.8563.