Caton, Donald (2000). "John Snow's practice of obstetric anesthesia". Anesthesiology: The Journal of the American Society of Anesthesiologists. 92 (1): 247–252. doi:10.1097/00000542-200001000-00037. PMID10638922.
nih.gov
pubmed.ncbi.nlm.nih.gov
Caton, Donald (2000). "John Snow's practice of obstetric anesthesia". Anesthesiology: The Journal of the American Society of Anesthesiologists. 92 (1): 247–252. doi:10.1097/00000542-200001000-00037. PMID10638922.