@article{Tandberg2007,
author = {Tandberg, A. and Bjørge, T. and Børdahl, P.E. and Skjaerven, R.},
title= {Increasing twinning rates in Norway, 1967-2004: The influence of maternal age and assisted reproductive technology (ART)},
year = {2007},
doi = {10.1080/00016340701417323},
journal = {Acta Obstetricia Et Gynecologica Scandinavica},
volume = {86},
number = {7},
pages = {833--839},
}