@article{Frątczak1999,
author = {Frątczak, E. and Ptak-Chmielewska, A.},
title= {Bongaarts-Feeney’s formula: an application for Poland},
year = {1999},
journal = {Studia Demograficzne},
volume = {2},
number = {136},
pages = {43--62},
}