@misc{indiciae24119ee4a086,
  title = {Bäcklund transformations and nonlinear differential difference equations.},
  author = {D Levi and R Benguria},
  year = {1980},
  doi = {10.1073/pnas.77.9.5025},
  url = {https://pubmed.ncbi.nlm.nih.gov/16592867/},
  note = {Source identifier: 16592867}
}