@article{Willekens1999,
author = {Willekens, F.},
title= {Modelling approaches to the indirect estimation of migration flows: From entropy to EM},
year = {1999},
doi = {10.1080/08898489909525459},
journal = {Mathematical Population Studies: An International Journal of Mathematical Demography},
volume = {7},
number = {3},
pages = {239--278},
}