APA (7th ed.) Citation

Malthus, T. R. (1970). An essay on the principle of population. Penguin Books.

Chicago Style (17th ed.) Citation

Malthus, T. R. An Essay on the Principle of Population. Harmondsworth: Penguin Books, 1970.

MLA (9th ed.) Citation

Malthus, T. R. An Essay on the Principle of Population. Penguin Books, 1970.

Warning: These citations may not always be 100% accurate.