@article{ziyuan2013an,
  title = {An input-output approach to evaluate the water footprint and virtual water trade of Beijing, China}
  author = {Ziyuan Wang and Kai Huang and Shunshun Yang and Yajuan Yu},
  journal = {Journal of Cleaner Production},
  doi = {10.1016/j.jclepro.2012.11.007},
  year = {2013}
}