Cita APA (7a ed.)

Simak Clifford D., 1. (1967). Time and Again. Penguin Books.

Cita Chicago Style (17a ed.)

Simak Clifford D., 1904. Time and Again. Middlesex: Penguin Books, 1967.

Cita MLA (8a ed.)

Simak Clifford D., 1904. Time and Again. Penguin Books, 1967.