@book{ BA29475455, author = "Williams, J. Whitridge (John Whitridge) and Cunningham, F. Gary", title = "Williams obstetrics", publisher = "Appleton & Lange", year = "1997", edition = "20th ed. / F. Gary Cunningham ... [et al.]", URL = "https://ci.nii.ac.jp/ncid/BA29475455" }