APA (7th ed.) Citation

Friend, J. N. (1909). The theory of valency. Longmans, Green.

Chicago Style (17th ed.) Citation

Friend, J. Newton. The Theory of Valency. London: Longmans, Green, 1909.

MLA (8th ed.) Citation

Friend, J. Newton. The Theory of Valency. Longmans, Green, 1909.

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