@article{Harvald_2004,
title={The Danish Twin Registry: Past and Present},
volume={7},
ISSN={0000-0000},
url={http://dx.doi.org/10.1375/136905204774200451},
DOI={10.1375/136905204774200451},
number={4},
journal={Twin Research},
publisher={Cambridge University Press (CUP)},
author={Harvald,
Bent and Hauge,
Gudrun and Kyvik,
Kirsten Ohm and Christensen,
Kaare and Skytthe,
Axel and Holm,
Niels V.},
year={2004},
month=aug,
pages={318–335} }