About: http://webisa.webdatacommons.org/228446283

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	the sum of the distances from (x,y) to 2 fixed pts, called the foci, is a constant.
http://www.w3.org/ns/prov#wasQuotedFrom	calculus7.com