@misc{indiciaeca87433a8f4d,
  title = {An immunization model for a heterogeneous population.},
  author = {H W Hethcote},
  year = {1978},
  doi = {10.1016/0040-5809(78)90011-4},
  url = {https://pubmed.ncbi.nlm.nih.gov/751264/},
  note = {Source identifier: 751264}
}