@misc{indiciaec4d95842909a,
  title = {THE SINGULARITIES OF INTEGRABLE STRUCTURALLY STABLE PFAFFIAN FORMS.},
  author = {I Kupka},
  year = {1964},
  doi = {10.1073/pnas.52.6.1431},
  url = {https://pubmed.ncbi.nlm.nih.gov/16591241/},
  note = {Source identifier: 16591241}
}