APA (7th ed.) Citation

Beard, R. E., Pesonen, E., & Pentikäinen, T. (1969). Risk theory. Methuen.

Chicago Style (17th ed.) Citation

Beard, R. E., E. Pesonen, and Teivo Pentikäinen. Risk Theory. London: Methuen, 1969.

MLA (8th ed.) Citation

Beard, R. E., et al. Risk Theory. Methuen, 1969.