@article{guo2014an,
  title = {An integrated material metabolism model for stocks of urban road system in Beijing, China}
  author = {Guo, Zhen; Hu, Dan; Zhang, Fuhua; Huang, Guolong; Xiao, Qiang},
  journal = {Science of The Total Environment},
  doi = {10.1016/j.scitotenv.2013.10.041},
  year = {2014}
}