It is unnecessary to use parenthetical citation after a direct quotation when the direct quotation is common knowledge.
Explanation:
The category of common knowledge items are proverbs or well known quotations, for example "to be or not to be" is a well known quotation that does not need to be followed by the name of the source.
Parenthetical citation is used to identify the source of the direct quotation, that is why they include the author's name and the page number if available.
