@article{Mercer2017,
author = {Mercer, A.W. and Kreuter, F. and Keeter, S. and Stuart, E.A.},
title= {Theory and practice in nonprobability surveys},
year = {2017},
doi = {10.1093/poq/nfw060},
volume = {81},
number = {S1},
pages = {250--271},
}