APA (7th ed.) Citation

Harper Collins, Harding, P., & Tomblin, G. (1996). How to identify trees. Harper Collins.

Chicago Style (17th ed.) Citation

Harper Collins, P. Harding, and G. Tomblin. How to Identify Trees. London: Harper Collins, 1996.

MLA (8th ed.) Citation

Harper Collins, et al. How to Identify Trees. Harper Collins, 1996.