@article{Mu:144779,
      author = {Mu, Song-lin and Zhang, Yi-feng and Wang, Kai-yong and  Tang, Cheng-cai and Wang, Ling-en and Liu, Yu},
      title = {{Valley Density Evaluation and Typical Development Pattern  in Mountainous Areas of Beijing}},
      journal = {Asian Agricultural Research},
      volume = {Volume 04},
      number = {Issue 12},
      pages = {33. - 6},
      year = {2012},
}