@misc{indiciae4caff30109dc,
  title = {Letter: Exercise testing in mitral valve disease.},
  author = {G B Marcus},
  year = {1974},
  doi = {10.1016/0002-9149(74)90142-8},
  url = {https://pubmed.ncbi.nlm.nih.gov/4414219/},
  note = {Source identifier: 4414219}
}