एपीए उद्धरण

Hawking,Stephen, & Penrose,Roger. (1999). The Nature of Space and Time. OUP.

शिकागो स्टाइल उद्धरण

Hawking,Stephen, और Penrose,Roger. The Nature of Space and Time. Delhi: OUP, 1999.

एमएलए उद्धरण

Hawking,Stephen, और Penrose,Roger. The Nature of Space and Time. OUP, 1999.