APA (7th ed.) Citation

Sandburg, C., Hendrick, G., & Hendrick, W. (1999). Poems for the people. I.R. Dee.

Chicago Style (17th ed.) Citation

Sandburg, Carl, George Hendrick, and Willene Hendrick. Poems for the People. Chicago: I.R. Dee, 1999.

MLA (8th ed.) Citation

Sandburg, Carl, et al. Poems for the People. I.R. Dee, 1999.