@article{Constant2011,
author = {Constant, A.F. and Zimmermann, K.F.},
title= {Circular and repeat migration: Counts of exits and years away from the host country},
year = {2011},
doi = {10.1007/s11113-010-9198-6},
volume = {30},
number = {4},
pages = {495--515},
}