@techreport{Kohler2001,
author = {Kohler, H.-P. and Skytthe, A. and Christensen, K.},
title= {The age at first birth and completed fertility reconsidered: Findings from a sample of identical twins},
year = {2001},
publisher = {Max Planck Institute for Demographic Research},
address = {Rostock},
number = {MPIDR Working Paper WP-2001-006},
}