@article{JMLR:v9:drton08a,
  author  = {Mathias Drton and Thomas S. Richardson},
  title   = {Graphical Methods for Efficient Likelihood Inference in Gaussian Covariance Models},
  journal = {Journal of Machine Learning Research},
  year    = {2008},
  volume  = {9},
  number  = {29},
  pages   = {893--914},
  url     = {http://jmlr.org/papers/v9/drton08a.html}
}