APA (7th ed.) Citation

Spence, W., & Kirby, W. (2013). An Introduction to Entomology: Vol. II (of 4) or Elements of the Natural History of the Insects. Project Gutenberg.

Chicago Style (17th ed.) Citation

Spence, William, and William Kirby. An Introduction to Entomology: Vol. II (of 4) or Elements of the Natural History of the Insects. Project Gutenberg, 2013.

MLA (9th ed.) Citation

Spence, William, and William Kirby. An Introduction to Entomology: Vol. II (of 4) or Elements of the Natural History of the Insects. Project Gutenberg, 2013.

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