1. Cunningham FG, Leveno KJ, Bloom SL, Hauth JC, Gilstrap III LC, Wenstrom KD. Abortion. In: Cunningham FG, Williams JW, editors. Williams obstetrics. 22 ed. New York: McGraw Hill; 2005. p. 231-51.
2. Christiansen OB. Epidemiology of recurrent pregnancy loss. In: Carp HJA, editor. Recurrent pregnancy loss causes, controversies and treatment. 1 ed. London: Informa Healthcare; 2007. p. 1-13.
3. Luisi S, Lazzeri L, Genazzani AR. Endocrinology of pregnancy loss. In: Carp HJA, editor. Recurrent Pregnancy loss causes, controversies and treatment. London: Informa Healthcare; 2007. p. 79-87.
4. Insight into Early Pregnancy Events: The Emerging Role of the Embryo*
5. Rosevear S. Bleeding in early pregnancy. In: James DK SJ, Weiner CP, Gonik B, editors. High Risk Pregnancy Management Options. 2nd ed. London: WB. Saunders; 2000. p. 61-89.