@article{xue2015municipal,
  title = {Municipal solid waste collection optimization in Singapore}
  author = {Xue, Weijian; Cao, Kai; Li, Wenwen},
  url = {https://www.sciencedirect.com/science/article/abs/pii/S0143622815000855},
  doi = {10.1016/j.apgeog.2015.04.002},
  year = {2015}
}