APA (7th ed.) Citation

Gray, H. L. (1915). English field systems. Harvard university press; [etc., etc.].

Chicago Style (17th ed.) Citation

Gray, Howard Levi. English Field Systems. Cambridge: Harvard university press; [etc., etc.], 1915.

MLA (9th ed.) Citation

Gray, Howard Levi. English Field Systems. Harvard university press; [etc., etc.], 1915.