Assertion: memory foam | /r/AtLocation | various forms
Facets:
value: since the midpoint of the century
type: TEMPORAL
Source sentences:
text: Though it is a relatively recent phenomenon in the US, memory foam has been around in various forms since the midpoint of the century—the first work on the polyurethane polymers that go into memory foam was actually begun in 1937 by Otto Bayer and his coworkers