@misc{W2007321142,
  author = {Leonard E. Baum and Ted Petrie},
  title = {Statistical Inference for Probabilistic Functions of Finite State Markov Chains},
  year = {1966},
  howpublished = {The Annals of Mathematical Statistics},
  doi = {https://doi.org/10.1214/aoms/1177699147}
}