If it already has the souce before it like for example it says " According to blank "Evidence" You still have to put the parentheses even though it is still there.
The information about the Luggnaggians which the narrator
(Gulliver) offers to his audience (English people) is their traditional
customs. At some fact of the story, Gulliver gives his view on the way to
points of views of Luggnaggians by telling it in order to make his spectators
learn the conceivable errors of others and not to do it again.
