@misc{indiciae606de9332eb5,
  title = {Inequalities for Complex Linear Differential Systems of the Second Order.},
  author = {D C Lewis},
  year = {1952},
  doi = {10.1073/pnas.38.1.63},
  url = {https://pubmed.ncbi.nlm.nih.gov/16589054/},
  note = {Source identifier: 16589054}
}