|perfect_failure_ref =<ref name="Trussell 2011">{{مرجعاستشهاد كتاببكتاب|الأخير=Trussell|الأول=James|سنة=2011|chapter=Contraceptive efficacy|editor1-last=Hatcher|editor1-first=Robert A.|editor2-last=Trussell|editor2-first=James|editor3-last=Nelson|editor3-first=Anita L.|editor4-last=Cates|editor4-first=Willard Jr.|editor5-last= Kowal|editor5-first=Deborah|editor6-last=Policar|editor6-first=Michael S. (eds.)|عنوان=Contraceptive Technology|إصدار=20th revised|مكان=New York|ناشر=Ardent Media|isbn=978-1-59708-004-0|issn = 0091-9721|oclc=781956734|صفحات=779–863}} Table 26–1 = <span class="plainlinks">[http://www.contraceptivetechnology.org/wp-content/uploads/2013/09/CTFailureTable.pdf Table 3–2 Percentage of women experiencing an unintended pregnancy during the first year of typical use and the first year of perfect use of contraception, and the percentage continuing use at the end of the first year. United States.]</span> {{Webarchive|url=https://web.archive.org/web/20190831165303/http://www.contraceptivetechnology.org/wp-content/uploads/2013/09/CTFailureTable.pdf |date=31 أغسطس 2019}}</ref>
