You're right, short quotes and phrases aren't protected by copyright.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.
I know what I think a "citation" is but I'm not real sure that you do -- in my world a citation is string of words and numbers that factually, and specifically according to guidelines in the particular academic field, identifies the source of something, usually a writing. Citations are facts, and are not creative, and so for both reasons not copyrightable.
A "saying" IS copyrightable if it's long enough to pass the "modicum of creativity" test. Short sayings do not pass the test -- "short" and "modicum of creativity" being defined by whatever judge happens to hear your case should the author file suit against you.
The copyrightability of a "quote" and a "proverb" are evaluated the same as a "saying."
Whether any of the above is famous or not has no bearing on its copyrightability.
In sum, the shorter the work the more likely copyright does not attach.