Found in articles
元素 (數學)
and Its Foundations. Academic Press. 1997. ISBN 0-12-622760-8. p. 12 George Boolos. 24.243 Classical Set Theory (lecture) (Speech). 麻省理工學院. February 4
History of Mathematics: A Brief Course. John Wiley & Sons. Stone, 1971. Boolos and Jeffrey, 1974,1999:19. Minsky, 1967, p. 105. Gurevich, 2000:1, 3. 圖靈完整性（Turing