Cita APA (7th ed.)
Hawking, S. W., & Penrose, R. (2010). The nature of space and time (13th print.). Princeton University Press.
Cita Chicago (17th ed.)
Hawking, S. W., i Roger Penrose. The Nature of Space and Time. 13th print. Princeton, N.J.: Princeton University Press, 2010.
Cita MLA (9th ed.)
Hawking, S. W., i Roger Penrose. The Nature of Space and Time. 13th print. Princeton University Press, 2010.
Atenció: Aquestes cites poden no estar 100% correctes.