The history and clinical usefulness of Pi.
D002404:Catheterization / Q000295:instrumentation; D004106:Dilatation; D004534:Egypt; D005602:France; D005858:Germany; D006115:Greece; D049671:History, 18th Century; D049672:History, 19th Century; D049673:History, 20th Century; D049690:History, Ancient; D007557:Israel; D008433:Mathematics / Q000266:history; D013525:Surgical Instruments; D014894:Weights and Measures