Fischer-Rasmussen et al: Eur J Obstet Gynecol Reproduction Biol 1990; 38:19-24.
Keating A, Chez RA. Ginger Syrup as an Antiemetic in Early Pregnancy. Alternative Therapies in Health and Medicine 2002; Vo. 8, No. 5.
Merkel, RL: Am J Obstet Gynecol 1952;64:416-8.