@article{holte2017mm,
  title={MM: A bidirectional search algorithm that is guaranteed to meet in the middle},
  author={Holte, Robert C and Felner, Ariel and Sharon, Guni and Sturtevant, Nathan R and Chen, Jingwei},
  journal={Artificial Intelligence},
  volume={252},
  pages={232--266},
  year={2017},
  publisher={Elsevier}
}