1. Obstetrics: normal & problem pregnancies;Gabbe,1986
2. Placental localization by ultrasound;Edlestone;Clin Obstet Gynecol,1977
3. Transvaginal sonography;Timor-Tritsch,1987
4. The ultrasonographic diagnosis placenta previa: value of the post void scan;Williamson;JCU,1978
5. Placenta previa: false negative diagnoses;Laing;JCU,1981