Forms for Syllogisms
This Demonstration shows categorical propositions, syllogistic figures, and 256 syllogistic forms, of which 24 are valid syllogisms.
The letters A, E, I, and O have been used since the medieval schools to form mnemonic names for the forms as follows: "Barbara" stands for AAA, "Celarent" for EAE, and so on .
 L. Carroll, Symbolic Logic and the Game of Logic, New York: Dover Publications, 1958.
 I. M. Copi and C. Cohen, Introduction to Logic, 9th ed., New York: Macmillan Publications, 1994 pp. 214–218.
 J. M. BocheÃ Âski, A History of Formal Logic, 2nd ed. (I. Thoma, trans. and ed.), New York: Chelsea Publishing Company, 1970 p. 235.
 Wikipedia. "Syllogism." en.wikipedia.org/wiki/Syllogism.