Ultrasonic Appearance of a Ring Pessary

1. Jeffcoate TNA : Principles of Gynaecology. London, Butterworths, 1972, pp 888-892.

2. Romney SL , Gray MJ , Lettle AB , Merrill JA , Quilligan EJ , Stander RW : Gynecology and Obstetrics: The Health Care of Women. New York, McGraw-Hill Book Co., 1981, pp 967-971.