@article{JMLR:v16:he15a,
  author  = {Yangbo He and Jinzhu Jia and Bin Yu},
  title   = {Counting and Exploring Sizes of Markov Equivalence Classes of Directed Acyclic Graphs},
  journal = {Journal of Machine Learning Research},
  year    = {2015},
  volume  = {16},
  number  = {79},
  pages   = {2589--2609},
  url     = {http://jmlr.org/papers/v16/he15a.html}
}