@article{cattaruzza2016vehicle,
title={Vehicle routing problems with multiple trips},
author={Cattaruzza, Diego and Absi, Nabil and Feillet, Dominique},
journal={4OR},
volume={14},
number={3},
pages={223--259},
year={2016},
publisher={Springer Berlin Heidelberg},
doi = {http://dx.doi.org/10.1007/s10288-016-0306-2}
}