Cita APA (7a ed.)
Hawking, S. W., & Penrose, R. The Nature of Space and Time. Princeton University.
Cita estilo Chicago (17a ed.)
Hawking, Stephen W., y Roger Penrose. The Nature of Space and Time. Princeton, EUA: Princeton University.
Cita MLA (9a ed.)
Hawking, Stephen W., y Roger Penrose. The Nature of Space and Time. Princeton University.
Precaución: Estas citas no son 100% exactas.