Assertion: pencil's design | /r/HasProperty | patented in 19th and 20th centuries
Facets:
Source sentences:
text: Mechanical pencils were first used in the 18th century, with many designs patented in the 19th and 20th centuries.
text: Mechanical pencils were first used in the 18th century with many designs patented in the 19th and 20th centuries.