@article{Trussell1999,
author = {Trussell, J. and Vaughan, B. and Stanford, J.},
title= {Are all contraceptive failures unintended pregnancies?},
year = {1999},
doi = {10.2307/2991573},
journal = {Family Planning Perspectives },
volume = {31},
number = {5},
pages = {246−260},
}