Assertion: ballpoint pen's ink | /r/AtLocation | invention
Facets:
Source sentences:
text: In these inventions, the ink was placed in a thin tube whose end was blocked by a tiny ball, held so that it could not slip into the tube or fall out of the pen.
text: In these inventions, the ink was placed in a thin tube whose end was blocked by a tiny ball, held so that it could not slip into the tube or fall out of the pen.