@article{Bates2015,
author = {Bates, D. and Mächler, M. and Bolker, B. and Walker, S.},
title= {Fitting linear mixed-effects models using Lme4},
year = {2015},
doi = {10.18637/jss.v067.i01},
volume = {67},
number = {1},
pages = {1--48},
}