APA (7th ed.) Citation

Christie, A. (1927). The big four. W. Collins sons & co., ltd.

Chicago Style (17th ed.) Citation

Christie, Agatha. The Big Four. London [etc]: W. Collins sons & co., ltd, 1927.

MLA (9th ed.) Citation

Christie, Agatha. The Big Four. W. Collins sons & co., ltd, 1927.

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