1. Nemes, G. and Kerenyi, T. D. (1971). Ultrasonic localization of the IUD: A new technique. Am. J. Obstet. Gynecol., 109, 1219
2. Schmidt, E. H., Quakernack, K. and Lieder, B. et al. (1975). Ultraschalluntersuchungen zur Lokalisation von Intrauterinepessaren im Modellversuch und an Patientinnen. Arch. Gynäkol., 218, 173
3. McArdle, C.R. (1978). Ultrasonic localization of missing intrauterine contraceptive devices. Obstet. Gynecol., 51, 330
4. Nelson, L. H. and Miller, J. B. (1979). Real-time ultrasound in locating intrauterine contraceptive devices. Obstet. Gynecol., 54, 711
5. Reiertsen, O. (1981). Real-time ultrasonography for location of IUDs. Contracept. Deliv. Syst., 2, 163