@article{Frejka2006a,
author = {Frejka, T. and Sardon, J.-P.},
title= {First birth trends in developed countries: persisting parenthood postponement},
year = {2006a},
doi = {10.4054/DemRes.2006.15.6},
URL = {http://www.demographic-research.org},
journal = {Demographic Research},
volume = {15},
number = {6},
pages = {147--180},
}