@article{zhen2013an,
  title = {An integrated material metabolism model for stocks of Urban road system in Beijing, China}
  author = {Zhen Guo, Dan Hu, Fuhua Zhang, Guolong Huang, Qiang Xiao},
  journal = {Science of The Total Environment},
  doi = {10.1016/j.scitotenv.2013.10.041},
  year = {2013}
}