एपीए उद्धरण

Hawking, S. P. Nature of space and time. OUP.

शिकागो स्टाइल उद्धरण

Hawking, Stephen Penrose. Nature of Space and Time. OUP.

एमएलए उद्धरण

Hawking, Stephen Penrose. Nature of Space and Time. OUP.