@article{PetBuh14,
  title = {Identifiability of {G}aussian Structural Equation Models with Equal Error Variances},
  journal = {Biometrika},
  volume = {101},
  number = {1},
  pages = {219--228},
  year = {2014},
  author = {Peters, J. and B{\"u}hlman, P.},
  doi = {10.1093/biomet/ast043}
}