See for example:
Sharpe, Alfred. "Doubt". The Catholic Encyclopedia, Vol. 5 (New York: Robert Appleton). http://www.newadvent.org/cathen/05141a.htm. பார்த்த நாள்: 2008-10-21. "A state in which the mind is suspended between two contradictory propositions and unable to assent to either of them."
Schulte, Karl Joseph (1910). "George Hermes". The Catholic Encyclopedia7. New York: Robert Appleton. அணுகப்பட்டது 2008-10-21.
