Statements that are still true must be
expressed in the present tense. Statements that
used to be true but that are no longer
true because facts or circumstances have changed
should be expressed in the past tense.
Ancient people thought the world was
flat. (not true)
Columbus knew the world is round.
I noticed that the report had many
typographical errors. (the errors have been
I noticed that the report introduces
many new ideas. (the report still does introduce
many new ideas)