Editing Markov blanket (section)

=== Uniqueness of Markov boundary ===
The Markov boundary always exists. Under some mild conditions, the Markov boundary is unique. However, for most practical and theoretical scenarios multiple Markov boundaries may provide alternative solutions.<ref>{{cite journal |last1=Statnikov |first1=Alexander |last2=Lytkin |first2=Nikita I. |last3=Lemeire |first3=Jan |last4=Aliferis |first4=Constantin F. |title=Algorithms for discovery of multiple Markov boundaries |journal=Journal of Machine Learning Research |date=2013 |volume=14 |pages=499-566 |url=http://www.jmlr.org/papers/volume14/statnikov13a/statnikov13a.pdf}}</ref> When there are multiple Markov boundaries, quantities measuring causal effect could fail.<ref>{{cite journal |last1=Wang |first1=Yue |last2=Wang |first2=Linbo |title=Causal inference in degenerate systems: An impossibility result |journal=Proceedings of the 23rd International Conference on Artificial Intelligence and Statistics |date=2020 |pages=3383-3392 |url=http://proceedings.mlr.press/v108/wang20i.html}}</ref>