@article{Bergstrand1983,
author = {Bergstrand, R. and Vedin, A. and Wilhelmsson, C. and Wilhelmsen, L.},
title= {Bias due to non-participation and heterogenous sub-groups in population surveys},
year = {1983},
doi = {10.1016/0021-9681(83)90166-2},
journal = {Journal of Chronic Diseases},
volume = {36},
number = {10},
pages = {725--728},
}