@article{sawada1972,
  title={Impurity Problem in the Ising Model},
  author={K. Sawada and Takeo Osawa},
  year={1972},
  journal={Progress of Theoretical Physics},
  doi={10.1143/ptp.47.1438},
  url={https://doi.org/10.1143/ptp.47.1438}
}