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APA Citation
Ward, R. H., Modell, B., Petrou, M., Karagözlu, F., & Douratsos, E. (1983). method of sampling chorionic villi in first trimester of pregnancy under guidance of real time ultrasound.. BMJ, 286(6377), 1542–1544. http://access.bl.uk/ark:/81055/vdc_100139599981.0x00002d