APA (7th ed.) Citation

Keegan, J., Holmes, R., Gau, J., & Forsyth, F. (1987). Soldiers: A history of men in battle. Sphere Books.

Chicago Style (17th ed.) Citation

Keegan, John, Richard Holmes, John Gau, and Frederick Forsyth. Soldiers: A History of Men in Battle. London: Sphere Books, 1987.

MLA (9th ed.) Citation

Keegan, John, et al. Soldiers: A History of Men in Battle. Sphere Books, 1987.