equaling the small Veblen ordinal(英语:small Veblen ordinal) (sometimes confused with the smaller Ackermannordinal(英语:Ackermannordinal)).[來源請求] Suppose that
philosophical logic (2nd ed.). 13 volumes. Dordrecht, Kluwer. D. Hilbert and W. Ackermann, 1928. Grundzüge der theoretischen Logik (Principles of Theoretical Logic)
Press. The first appearance of quantification. David Hilbert and Wilhelm Ackermann, 1950 (1928). Principles of Theoretical Logic. Chelsea. Translation of
Chicago Press) and New York: Seven Bridges Press. David Hilbert and Wilhelm Ackermann 1950. Principles of Theoretical Logic(English translation). Chelsea. The