Assertion: different chemical | /r/HasProperty | stockpiled as chemical warfare agents
Facets:
value: during the 20th century
type: TEMPORAL
Source sentences:
text: About 70 different chemicals have been used or stockpiled as chemical warfare agents during the 20th century.
text: About 70 different chemicals have been used or stockpiled as chemical warfare agents during the 20th and 21st centuries.