Whitehead, A. N. (1927). Principia mathematica: To 56. C.U.Pr.
Cita Chicago (17th ed.)Whitehead, Alfred North. Principia Mathematica: To 56. Cambridge: C.U.Pr, 1927.
Cita MLA (9th ed.)Whitehead, Alfred North. Principia Mathematica: To 56. C.U.Pr, 1927.
Atenció: Aquestes cites poden no estar 100% correctes.