Cita APA (7a ed.)

Gingrich, N., & Maple, T. (2007). A Contract with the Earth. Johns Hopkins University Press.

Cita Chicago Style (17a ed.)

Gingrich, Newt, y Terry Maple. A Contract with the Earth. Baltimore: Johns Hopkins University Press, 2007.

Cita MLA (8a ed.)

Gingrich, Newt, y Terry Maple. A Contract with the Earth. Johns Hopkins University Press, 2007.