APA (7th ed.) Citation

Prior, Wilson, & Keegan. (2001). The first World War. Cassell & Co.

Chicago Style (17th ed.) Citation

Prior, Wilson, and Keegan. The First World War. Great Britain: Cassell & Co, 2001.

MLA (8th ed.) Citation

Prior, et al. The First World War. Cassell & Co, 2001.