APA (7th ed.) Citation

Friend, J. N. (1915). The theory of valency (2d ed., rev.). Longmans, Green.

Chicago Style (17th ed.) Citation

Friend, J. Newton. The Theory of Valency. 2d ed., rev. London, New York [etc.]: Longmans, Green, 1915.

MLA (9th ed.) Citation

Friend, J. Newton. The Theory of Valency. 2d ed., rev. Longmans, Green, 1915.