APA (7th ed.) Citation

Gibson, H. H., & Maxwell, H. (2013). American Forest Trees. Project Gutenberg.

Chicago Style (17th ed.) Citation

Gibson, Henry H., and Hu Maxwell. American Forest Trees. Project Gutenberg, 2013.

MLA (9th ed.) Citation

Gibson, Henry H., and Hu Maxwell. American Forest Trees. Project Gutenberg, 2013.

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