Citação norma APA

Sagan, C. (1997). Billions and billions: Thoughts on life and death at the brink of the millennium. Headline Book Publishing.

Citação norma Chicago

Sagan, Carl. Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium. London: Headline Book Publishing, 1997.

Citação norma MLA

Sagan, Carl. Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium. Headline Book Publishing, 1997.

Nota: a formatação da citação pode não corresponder 100% ao definido pela respectiva norma.