Assertion: bone charcoal | /r/ObjectUse | used in the united states
Facets:
value: from the 1940s
type: TEMPORAL
value: widely
type: DEGREE
value: through to the 1960s
type: TEMPORAL
Source sentences:
text: Bone charcoal is the oldest known water defluoridation agent and was widely used in the United States from the 1940s through to the 1960s.