@article{Hug2003,
author = {Hug, S.},
title= {Selection bias in comparative research: The case of incomplete data sets},
year = {2003},
doi = {10.1093/pan/mpg014},
URL = {https://doi.org/10.1093/pan/mpg014},
volume = {11},
number = {3},
pages = {255--274},
}